Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Genome mutation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58Linked to original sources
PubMed2025

Genomic signature and evolutionary history of completely cleistogamous lineages in the non-photosynthetic orchid Gastrodia.

Despite a long-standing interest since Darwin's time, the genomic implications of obligate self-fertilization remain elusive. Complete cleistogamy-the obligate production of closed, self-pollinating flowers-represents an extreme reproductive strategy. Here, we present the genomic profiles and evolutionary history of two lineages of the mycoheterotrophic orchid Gastrodia, both of which independently acquired complete cleistogamy, based on detailed sampling and a combination of simple sequence repeat (SSR), multiplexed ISSR genotyping by sequencing (MIG-seq) and RNA-seq data. Our analysis reveals clear species delimitation, with no evidence of introgression between the completely cleistogamous species and their co-occurring allogamous sisters. Intriguingly, all analyses indicate that both the completely cleistogamous Gastrodia species and their allogamous sisters exhibit genetic profiles typical of self-pollinating plants. This pattern suggests that their ancestors, probably bearing allogamous flowers, had already evolved mechanisms to mitigate the deleterious effects of selfing, potentially facilitating the emergence of complete cleistogamy through benefits such as reproductive assurance, enhanced colonization ability and species reinforcement. Meanwhile, further analyses suggest that complete cleistogamy evolved very recently (possibly within the last 1000-2000 years) in these two Gastrodia lineages. Combined with the scant evidence of complete cleistogamy outside Gastrodia, our findings imply a limited and ephemeral role for complete cleistogamy in plant speciation.

Biological Evolution↗
PubMed2002

[Molecular cloning of the human CX 58 gene].

OBJECTIVE: To clone a novel human connexin gene and find out the relationship between this gene and hereditary deafness. METHODS: Through the basic local alignment search tool (BLAST) analysis against the database of expressed sequence tags (dbEST) of National Center for Biotechnology Information (NCBI) using the coding sequence of mouse Cx 57 gene, 9 novel ESTs were obtained and a contig was assembled. Nested polymerase chain reaction (PCR) and rapid amplification of cDNA ends (RACE) were performed using primers designed on the contig. A novel gene was obtained and was mapped by homologous analysis against human genome sequence. Mutation analysis was performed in 12 autosomal dominant hereditary deafness families. RESULTS: Nine ESTs were obtained by homologous analysis and a contig was assembled. Through nested PCR and RACE, a full length of cDNA was obtained from human liver, kidney Ready cDNA and placenta cDNA library, and was named CX 58. By comparison with human genome sequence, CX 58 was mapped at 1p32.3-p34.1. Mutation analysis of CX 58 was performed in 12 autosomal dominant hereditary deafness families, but no mutation was detected. CONCLUSION: A novel human connexin gene named CX 58 was cloned and mapped to 1p32.3-p34.1. The mutation of CX 58 may not result in autosomal dominant hereditary deafness.

Animals↗
PubMed2005

Mutation rate variation at human dinucleotide microsatellites.

Mutation is the ultimate source of genetic variation, and mutation rate is thus an important parameter governing the extent of genetic variation. Microsatellites are highly informative genetic markers that have been widely used in genetic studies. While previous studies showed that the mutation rate differs in di-, tri-, and tetranucleotide repeats, how mutation rate distributes within each class of repeat is poorly understood. This study first revealed the pattern of the mutation rate variation within the dinucleotide repeats. Two data sets were used. The first is the allele frequency data from 115 microsatellites with dinucleotide repeats distributed along the human genome in 10 worldwide populations. The second data set is much larger, consisting of the allele frequency of 5252 dinucleotide repeats from the Genome Database. Mutation rate for each locus is estimated through a new homozygosity-based estimator, which has been shown to be unbiased and highly efficient and is reasonably robust against deviations from the single-step model. The mutation rates among loci can be approximated well by a gamma distribution and its shape parameter can be accurately estimated with this approach. This result provides the basic guidelines for analyzing the large-scale genomic data from microsatellite loci.

Alleles↗
PubMed2002

Rates and patterns of molecular evolution in inbred and outbred Arabidopsis.

The evolution of self-fertilization is associated with a large reduction in the effective rate of recombination and a corresponding decline in effective population size. If many spontaneous mutations are slightly deleterious, this shift in the breeding system is expected to lead to a reduced efficacy of natural selection and genome-wide changes in the rates of molecular evolution. Here, we investigate the effects of the breeding system on molecular evolution in the highly self-fertilizing plant Arabidopsis thaliana by comparing its coding and noncoding genomic regions with those of its close outcrossing relative, the self-incompatible A. lyrata. More distantly related species in the Brassicaceae are used as outgroups to polarize the substitutions along each lineage. In contrast to expectations, no significant difference in the rates of protein evolution is observed between selfing and outcrossing Arabidopsis species. Similarly, no consistent overall difference in codon bias is observed between the species, although for low-biased genes A. lyrata shows significantly higher major codon usage. There is also evidence of intron size evolution in A. thaliana, which has consistently smaller introns than its outcrossing congener, potentially reflecting directional selection on intron size. The results are discussed in the context of heterogeneity in selection coefficients across loci and the effects of life history and population structure on rates of molecular evolution. Using estimates of substitution rates in coding regions and approximate estimates of divergence and generation times, the genomic deleterious mutation rate (U) for amino acid substitutions in Arabidopsis is estimated to be approximately 0.2-0.6 per generation.

Arabidopsis↗
PubMed2002

DNA hypermethylation: when tumour suppressor genes go silent.

The phenotype of the cancerous cell may arise either from genetic alterations that disrupt gene function through sequence modifications (mutations) or epigenetic events that may alter the heritable state of gene expression (i.e. without changing the actual sequence of the genome). Whereas mutations in certain tumour suppressor genes are most often thought of in association with their inactivation during cancer initiation or progression, epigenetic alterations such as DNA methylation appear to be tightly linked to the sequential non-reversible events of normal tissue differentiation and organogenesis. This highlights a link between tissue differentiation and tumourigenesis with respect to the stable nature of certain epigenetic changes. In the case of tumourigenesis, both genetic and epigenetic mechanisms of altered gene expression often go hand in hand; not surprisingly, biallelic inactivation of a given tumour suppressor gene may occur via a combination of mutational and epigenetic events and is entirely consistent with the Knudson two-hit hypothesis of tumourigenesis. This review summarizes recent developments within the field of DNA methylation, highlighting its association with the transcriptional silencing of tumour suppressor genes in a variety of human cancers.

CpG Islands↗
PubMed2002

Histologic-genetic mapping by allele-specific PCR reveals intraurothelial spread of p53 mutant tumor clones.

Common and clinically important features of urothelial carcinomas are multifocality and a high rate of recurrence. Molecular studies demonstrated that multifocal tumors are frequently composed of one tumor clone spreading throughout the urothelial tract. A combination of histologic and genetic mapping of cystectomy specimens from bladder cancer patients is a valuable tool to study bladder carcinogenesis and tumor cell spread by correlating urothelial morphologic features and defined genetic alterations. In the present study, the primary tumors of 14 cystectomy specimens were investigated for p53 protein overexpression by immunohistochemistry and p53 gene mutation by genomic sequencing. Seven tumors showed a strong nuclear staining for the p53 protein. In six of seven tumors, a p53 gene mutation was detected. Allele-specific PCR of defined p53 mutations was established in five of six cases with a p53 mutation. Subsequent screening of the entire urothelial lining of each cystectomy specimen by allele-specific PCR revealed p53-mutant cell clones in urothelial patches with carcinoma in situ and dysplasia, but also frequently in histomorphologically normal urothelium adjacent to the tumor. The pattern of tumor cell spread indicated a continuous intraurothelial growth of the p53-mutant clone. P53 immunohistochemistry visually confirmed the presence of mutant cells in most of these samples. We conclude that allele-specific PCR is a highly sensitive and reliable method for tracking specific p53 mutant clones in the urothelium. Moreover, the detection of p53-mutant cells in histologically normal or preneoplastic urothelial areas in four patients with invasive bladder cancer indicates an extensive intraurothelial tumor cell spread. The excellent correlation of immunohistochemically positive urothelial patches with the presence of a specific mutation highlights the biologic significance of p53-positive cells in the urothelium of tumor patients.

Aged↗
PubMed1999

In vivo addition of poly(A) tail and AU-rich sequences to the 3' terminus of the Sindbis virus RNA genome: a novel 3'-end repair pathway.

Alphaviruses are mosquito-transmitted RNA viruses that cause important diseases in both humans and livestock. Sindbis virus (SIN), the type species of the alphavirus genus, carries a 11.7-kb positive-sense RNA genome which is capped at its 5' end and polyadenylated at its 3' end. The 3' nontranslated region (3'NTR) of the SIN genome carries many AU-rich motifs, including a 19-nucleotide (nt) conserved element (3'CSE) and a poly(A) tail. This 3'CSE and the adjoining poly(A) tail are believed to regulate the synthesis of negative-sense RNA and genome replication in vivo. We have recently demonstrated that the SIN genome lacking the poly(A) tail was infectious and that de novo polyadenylation could occur in vivo (K. R. Hill, M. Hajjou, J. Hu, and R. Raju, J. Virol. 71:2693-2704, 1997). Here, we demonstrate that the 3'-terminal 29-nt region of the SIN genome carries a signal for possible cytoplasmic polyadenylation. To further investigate the polyadenylation signals within the 3'NTR, we generated a battery of mutant genomes with mutations in the 3'NTR and tested their ability to generate infectious virus and undergo 3' polyadenylation in vivo. Engineered SIN genomes with terminal deletions within the 19-nt 3'CSE were infectious and regained their poly(A) tail. Also, a SIN genome carrying the poly(A) tail but lacking a part or the entire 19-nt 3'CSE was also infectious. Sequence analysis of viruses generated from these engineered SIN genomes demonstrated the addition of a variety of AU-rich sequence motifs just adjacent to the poly(A) tail. The addition of AU-rich motifs to the mutant SIN genomes appears to require the presence of a significant portion of the 3'NTR. These results indicate the ability of alphavirus RNAs to undergo 3' repair and the existence of a pathway for the addition of AU-rich sequences and a poly(A) tail to their 3' end in the infected host cell. Most importantly, these results indicate the ability of alphavirus replication machinery to use a multitude of AU-rich RNA sequences abutted by a poly(A) motif as promoters for negative-sense RNA synthesis and genome replication in vivo. The possible roles of cytoplasmic polyadenylation machinery, terminal transferase-like enzymes, and the viral polymerase in the terminal repair processes are discussed.

3' Untranslated Regions↗
PubMed2004

[The main effect of chromosomal rearrangement is changing the action of regulatory genes].

Effect of chromosomal rearrangements on the expression of mutations was studied in Drosophila melanogaster regulatory genes. These were facultative dominant lethals and recessive lethals on the X chromosome obtained by the classical Muller-5 method. Chromosomal rearrangements drastically changed the expression of regulatory gene mutations. Rearrangements either caused the lethal effect of mutations or suppressed the already present lethality. The action of rearrangements exhibited the maternal or paternal effect. Irrespective of the presence in the genome of mutations at regulatory genes, a rearrangement acted as a factor decreasing fertility of the organism. The rearrangement effect is identical to the expression of regulatory genes per se. It is concluded that the chromosomal rearrangement affects the examined regulatory genes indirectly through a change in the operation of regulatory genes located within the rearrangement. Thus, rearrangements gain great importance for the definition of the pattern of genome functional activity. Widespread distribution of rearrangements in individual genotypes and their effectivity in the process of speciation are thus explained.

Animals↗
PubMed1989

An improved host-vector system for Candida maltosa using a gene isolated from its genome that complements the his5 mutation of Saccharomyces cerevisiae.

The host-vector system of an n-alkane-assimilating-yeast, Candida maltosa, which we previously constructed using an autonomously replicating sequence (ARS) region isolated from the genome of this yeast, utilizes C. maltosa J288 (leu2-) as a host. As this host had a serious growth defect on n-alkane, we developed an improved host-vector system using C. maltosa CH1 (his-) as host. The vectors were constructed with the Candida ARS region and a DNA fragment isolated from the genome of C. maltosa. Since this DNA fragment could complement histidine auxotrophy of both C. maltosa CH1 and S. cerevisiae (his5-), we termed the gene contained in this DNA fragment C-HIS5. The vectors were characterized in terms of transformation frequency and stability, and the nucleotide sequence of C-HIS5 was determined. The deduced amino acid sequence (389 residues) shared 51% homology with that of HIS5 of S. cerevisiae (384 residues; Nishiwaki et al. 1987).

Base Sequence↗
PubMed1994

Optimal infectivity in vitro of human immunodeficiency virus type 1 requires an intact nef gene.

The replication competence of human immunodeficiency virus type 1 genomes containing mutations in the nef open reading frame was evaluated in continuous cell lines. Mutants that contained a deletion in the nef open reading frame, premature termination codons, or missense mutations in the N-terminal myristoylation signal were constructed. The replication of these mutants was tested in three ways. First, plasmid genomes were used to transfect T-lymphoblastoid cells. Second, low-passage posttransfection supernatants were used to infect cells with a relatively low virus input. Third, high-titer virus stocks were used to infect cells with a relatively high virus input. These experiments demonstrated a 100- to 10,000-fold decrement in p24 production by the nef mutants compared with that by the wild-type virus. The greatest difference was obtained after infection with the lowest virus input. The myristoylation signal was critical for this positive effect of nef. To investigate the mechanism of the positive influence of nef, nef-positive and nef-minus viruses were compared during a single cycle of replication. These single-cycle experiments were initiated both by infection with high-titer virus stocks and by transfection with viral DNA. Single-cycle infection yielded a three- to fivefold decrement in p24 production by nef-minus virus. Single-cycle transfection yielded equal amounts of p24 production. These results implied that nef does not affect replication after the provirus is established. In support of these results, viral production from cells chronically infected with nef-positive or nef-minus viruses was similar over time. To determine whether the effect of nef was due to infectivity, end point titrations of nef-positive and nef-minus viruses were performed. nef-positive virus had a greater infectivity per picogram of HIV p24 antigen than nef-minus virus. These data indicated that the positive influence of nef on viral growth rate is due to an infectivity advantage of virus produced with an intact nef gene.

Amino Acid Sequence↗
PubMed1993

Mosaicism in human skin. Understanding the patterns and mechanisms.

BACKGROUND: The skin is especially suitable for the study of mosaicism. In this review, the various genetic mechanisms leading to mosaicism and the resulting cutaneous patterns are considered. OBSERVATIONS: Mosaicism may produce different cutaneous patterns such as the lines of Blaschko, the checkerboard pattern, the phylloid pattern, and a patchy pattern without midline separation. A unique lateralization pattern is observed in the CHILD syndrome. Two major genetic categories are functional mosaics resulting from X inactivation and genomic mosaics caused by autosomal mutations. Functional mosaicism may be caused by either male-lethal or nonlethal X-linked mutations. Similarly, autosomal mutations resulting in genomic mosaicism may be either lethal or nonlethal. Many mosaics are caused by loss of heterozygosity, and uncommonly this mechanism may give rise to twin spots such as vascular twin nevi. Some cutaneous mosaic phenotypes virtually always occur sporadically, but exceptionally may show a familial aggregation. This paradox may be explained by paradominant inheritance. Heterozygous individuals are, as a rule, unaffected, but they express the birthmark when allelic loss occurs during embryogenesis. CONCLUSIONS: The concept of cutaneous mosaicism is important for gene mapping because here we have the opportunity to study two populations of cells differing only with regard to the mutation causing mosaicism. Future research will probably show that a specific genetic anomaly, when present as a mosaic, always produces the same type of cutaneous pattern.

Animals↗
PubMed2004

Leukaemia inhibitory factor (LIF) gene mutations in women with unexplained infertility and recurrent failure of implantation after IVF and embryo transfer.

OBJECTIVE: Leukaemia inhibitory factor (LIF) plays a central role in the control of implantation. We undertook this study to investigate the prevalence of LIF gene alterations in women with unexplained infertility and with recurrent failure of implantation after in vitro fertilisation (IVF) and embryo transfer. PATIENTS AND METHODS: Forty five women with recurrent failure of implantation after IVF (group A), 50 with unexplained infertility (group B) and 105 fertile women (controls) were screened for LIF gene mutations. Standard genomic DNA extraction, PCR amplification of the LIF gene and single-strand conformation polymorphism (SSCP) analysis were used to search for mutations which were subsequently confirmed by DNA sequencing. RESULTS: In group A, one woman was identified as having a neutral LIF gene polymorphism in exon 3 without affecting protein conformation. In group B, one woman with a heterozygous mutation and one with a neutral polymorphism were detected. In controls, only one woman with a neutral polymorphism in the intron between exons 2 and 3 was found. The woman with a potentially functional LIF gene mutation in group B achieved an ongoing clinical pregnancy after ovarian superovulation. DISCUSSION: Potentially functional mutations in the LIF gene do infrequently occur in women with unexplained infertility and may play a role in the etiology of infertility. However, routine screening for LIF mutations or polymorphisms in these women is not justified for the low prevalence of gene alterations.

Abortion, Habitual↗
PubMed2005

Evolution of proteins and gene expression levels are coupled in Drosophila and are independently associated with mRNA abundance, protein length, and number of protein-protein interactions.

Organismic evolution requires that variation at distinct hierarchical levels and attributes be coherently integrated, often in the face of disparate environmental and genetic pressures. A central part of the evolutionary analysis of biological systems remains to decipher the causal connections between organism-wide (or genome-wide) attributes (e.g., mRNA abundance, protein length, codon bias, recombination rate, genomic position, mutation rate, etc) as well as their role-together with mutation, selection, and genetic drift-in shaping patterns of evolutionary variation in any of the attributes themselves. Here we combine genome-wide evolutionary analysis of protein and gene expression data to highlight fundamental relationships among genomic attributes and their associations with the evolution of both protein sequences and gene expression levels. Our results show that protein divergence is positively coupled with both gene expression polymorphism and divergence. We show moreover that although the number of protein-protein interactions in Drosophila is negatively associated with protein divergence as well as gene expression polymorphism and divergence, protein-protein interactions cannot account for the observed coupling between regulatory and structural evolution. Furthermore, we show that proteins with higher rates of amino acid substitutions tend to have larger sizes and tend to be expressed at lower mRNA abundances, whereas genes with higher levels of gene expression divergence and polymorphism tend to have shorter sizes and tend to be expressed at higher mRNA abundances. Finally, we show that protein length is negatively associated with both number of protein-protein interactions and mRNA abundance and that interacting proteins in Drosophila show similar amounts of divergence. We suggest that protein sequences and gene expression are subjected to similar evolutionary dynamics, possibly because of similarity in the fitness effect (i.e., strength of stabilizing selection) of disruptions in a gene's protein sequence or its mRNA expression. We conclude that, as more and better data accumulate, understanding the causal connections among biological traits and how they are integrated over time to constrain or promote structural and regulatory evolution may finally become possible.

Animals↗
PubMed1989

A point mutation in the poliovirus polymerase gene determines a complementable temperature-sensitive defect of RNA replication.

We have previously described the isolation of a RNA- temperature-sensitive (ts) mutant of poliovirus type 1, ts035, after chemical mutagenesis by 5-fluorouracil. The ts defect of ts035 correlated with defective RNA replication, since the two characters corevert in the case of spontaneous revertants. The alteration of a trans-acting replication function of ts035 was suggested by significant rescue following mixed infection with another ts mutant, ts221, or with wild-type virus. Protein synthesis appeared normal at 39 degrees (nonpermissive temperature) in shift-up experiments and no defect of RNA elongation was evidenced when the activity of replication complexes or purified polymerase was measured at 39 degrees. These results provide circumstantial evidence that the initiation of ts035 RNA synthesis at 39 degrees is impaired. Molecular cloning of the ts035 genome allowed us to construct a recombinant virus with the same ts phenotype as ts035, by the transfer of a fragment of the mutant polymerase gene into the wild-type genome. Two mutations were present in this region of the ts035 genome but the determination of nucleotide sequences in the case of ts035 revertants indicated that only the substitution from A to G at nucleotide 7256 was necessary for the ts phenotype. This mutation replaces Asn 426 by an Asp in polypeptide 3D, the viral polymerase.

Base Sequence↗
PubMed1989

Detection of point mutations in amplified single copy genes by biotin-labelled oligonucleotides: diagnosis of variants of alpha-1-antitrypsin.

Specific analysis for point mutations in genomic DNA has until recently been a difficult and time-consuming task, using large amounts of unstable, hazardous and expensive 32P. By enzymatically amplifying the mutation-bearing sequence of the DNA the sensitivity of the analysis is increased several 100-fold, making the detection possible with stable, non-radioactive and inexpensive biotinylated oligonucleotides. We have applied this method (polymerase chain reaction (PCR] to the detection of the Z-mutation in the alpha-1-antitrypsin gene. After amplification, dot-blots of amplified DNA were subjected to hybridization with allele specific biotinylated oligonucleotide probes and washed at temperatures giving allele specificity. The bound biotin was visualized with avidin conjugated alkaline phosphatase using 5-bromo-4-chloro-3-indolylphosphate and nitro blue tetrazolium as colour reagents. The detection can be performed on less than 1 microgram genomic DNA, and is therefore applicable on small amounts of blood, fibroblasts and chorionic villus biopsies.

Base Sequence↗
PubMed2002

Mutational analysis of StAR gene in adrenal tumors.

Adrenal adenomas and carcinomas are mostly monoclonal, suggesting that a genetic alteration in a progenitor cell may contribute to their development. However, the molecular pathogenesis of these tumors still remains unclear. It has been already excluded that activating mutations of the ACTH receptor or of G protein stimulator alpha sub-units, affecting cAMP pathway, is involved in the tumorigenesis. Therefore, this work has been focused on post-transductional (ACTH) signal alterations and in particular on the mutational analysis of the Steroid Acute Regulatory protein (StAR) gene to verify whether somatic mutations or genomic polymorphisms of this gene may be correlated with adrenal tumorigenesis. Tissue DNA was extracted from 40 functional and non-functional adrenocortical tumors that were removed from patients aged between 17 and 72 years (mean 43 +/- 4). Blood DNA was obtained from 24 patients (aged between 26 and 70 years) affected by adrenal tumors and from 100 healthy subjects without radiological and clinical evidence of adrenal masses, aged between 25-35 years (90 Caucasians and 10 Africans). The DNA was used as the template for the amplification of the StAR gene using the polymerase chain reaction. The amplified DNA of each exon of the StAR gene was purified and sequenced in automatic sequenciator. With the exception of exon 5 showing in codon 203 an homozygous missense mutation, the sequence of the other exons of the StAR gene resulted normal in all tumors studied. The same homozygous mutation (Asp203Ala) was observed in the sequence of exon 5 performed on genomic DNA of the 24 affected patients and in the control subjects. The homozygosity of the mutation observed in all patients (either in tissue or blood samples) and in control subjects, independently of their ethnic origin, led us to suggest that the Asp203Ala cannot be considered as mutation or as polymorphism, but that it must be considered as a mistake in the sequence entered in the Genbank, which needs to be modified accordingly. These data, and those up to now reported in the literature, allow us to suggest that mutations of the gene coding for the protein involved in the initial step of the steroidogenesis could not be considered as a possible cause for the development of adrenal tumors.

Adenoma↗
PubMed2006

DNA damage checkpoints and cancer.

DNA damage checkpoint is one of the surveillance systems to maintain genomic integrity. Checkpoint systems sense the DNA damage and execute cell cycle arrest through inhibiting the activity of cell cycle regulators. This pathway is essential for the maintenance of genome stability and prevention of tumor development. Recent studies have showed that the cellular responses towards DNA damage, such as cell cycle arrest, DNA repair, chromatin remodeling, and apoptosis are well coordinated. Here we describe the molecular mechanisms of checkpoint activation in response to DNA damage and the correlation between checkpoint gene mutation and genomic instability.

Animals↗
PubMed1996

Role of the DIS hairpin in replication of human immunodeficiency virus type 1.

The virion-associated genome of human immunodeficiency virus type 1 consists of a noncovalently linked dimer of two identical, unspliced RNA molecules. A hairpin structure within the untranslated leader transcript is postulated to play a role in RNA dimerization through base pairing of the autocomplementary loop sequences. This hairpin motif with the palindromic loop sequence is referred to as the dimer initiation site (DIS), and the type of interaction is termed loop-loop kissing. Detailed phylogenetic analysis of the DIS motifs in different human and simian immunodeficiency viruses revealed conservation of the hairpin structure with a 6-mer palindrome in the loop, despite considerable sequence divergence. This finding supports the loop-loop kissing mechanism. To test this possibility, proviral genomes with mutations in the DIS palindrome were constructed. The appearance of infectious virus upon transfection into SupT1 T cells was delayed for the DIS mutants compared with that obtained by transfection of the wild-type provirus (pLAI), confirming that this RNA motif plays an important role in virus replication. Surprisingly, the RNA genome extracted from mutant virions was found to be fully dimeric and to have a normal thermal stability. These results indicate that the DIS motif is not essential for human immunodeficiency virus type 1 RNA dimerization and suggest that DIS base pairing does not contribute to the stability of the mature RNA dimer. Instead, we measured a reduction in the amount of viral RNA encapsidated in the mutant virions, suggesting a role of the DIS motif in RNA packaging. This result correlates with the idea that the processes of RNA dimerization and packaging are intrinsically linked, and we propose that DIS pairing is a prerequisite for RNA packaging.

Genome, Viral↗