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PubMed1997

The abundant latency-associated transcripts of herpes simplex virus type 1 are bound to polyribosomes in cultured neuronal cells and during latent infection in mouse trigeminal ganglia.

During herpes simplex virus type 1 (HSV-1) latency, limited viral transcription takes place. This transcription has been linked to the ability of the HSV-1 genome to reactivate and consists of abundant 2.0- and 1.5-kb collinear latency-associated transcripts (LATs), spanned by minor hybridizing RNA (mLAT). The 1.5-kb LAT is derived from the 2.0-kb LAT by splicing, and both transcripts contain two large overlapping open reading frames. The molecular action mechanisms of the latency-associated gene expression are unknown, and no HSV-1 latency-encoded proteins have been convincingly demonstrated. We have cloned the entire latency-associated transcriptionally active HSV-1 DNA fragment (10.4 kb) under control of a constitutive promoter and generated a neuronal cell line (NA4) stably transfected with the viral LAT's region. NA4 cells produced the 2.0- and the 1.5-kb LATs. Northern blotting and reverse transcription-PCR analysis of RNA from NA4 cells and from trigeminal ganglia of mice latently infected with HSV-1 revealed that the two abundant LAT species were present in the polyribosomal RNA fractions. After addition of EDTA, which causes dissociation of mRNA-ribosome complexes, both LATs could be detected only in subpolyribosomal, but not in polyribosomal fractions. These results show that (i) HSV-1 LATs are bound to polyribosomes during latency in vivo, as well as in neuronal cells in vitro, and therefore might be translated, and that (ii) the NA4 cell line is a suitable tool with which to look for HSV-1 latency-encoded gene products.

Animals↗
PubMed1980

Post-transcriptional regulation of messenger abundance in rat liver and hepatoma.

Saturation hybridisation with labelled single-copy DNA shows that polysomal poly(A)+ RNA of rat liver and of a minimum-deviation rat hepatoma cell-line (HTC) have similar total complexities and that few sequences are specific to either cell-type. Hybridisation kinetics of polysomal cDNAs with template and heterologous cell RNAs indicate that a proportion of liver messengers are at greatly reduced abundance in the hepatoma, but not the converse. Hybridisations using fractionated cDNAs enriched for abundant polysomal sequences confirm these findings: on average, abundant liver mRNAs are about 100-fold rarer in hepatoma, whereas abundant hepatoma mRNAs are only 5-fold rarer in liver. This pattern is also implied by cell-free translation of polysomal poly(A)+ RNAs. The reactions of total and fractionated polysomal cDNA probes with poly(A)+ nuclear RNA indicate that there is much less disparity in abundance of these sequences at nuclear level, implying that the differences arise, at least in part, post-transcriptionally. We interpret the altered mRNA abundances in the hepatoma in terms both of its decreased functional specialisation and its ability to proliferate.

Animals↗
PubMed1988

Concomitant transcriptional and post-transcriptional control of mRNA abundance during human myeloid cell differentiation.

The mechanisms controlling the expression of two genes during the differentiation of HL60 cells have been studied. The relative abundance of one mRNA, designated 2B5, increases during retinoic acid-induced differentiation; this increase can be accounted for, in part at least, by a marked increase in the rate of transcription of the gene. The relative abundance of the second, pCG56, decreases during retinoic acid-induced differentiation although the rate of transcription of this gene also increases during the course of differentiation. The bulk of pCG56 transcripts, though polyadenylated and apparently fully processed, are located in the nuclei of the uninduced cells, but on the polysomes of the induced cells. The data indicate that the change in the expression of the gene encoding pCG56 RNA is regulated differently from that encoding 2B5 RNA, and are interpreted as evidence that the pCG56 gene is regulated by an interaction between transcriptional and post-transcriptional controls. Furthermore, the latter includes both mRNA stability and a post-transcriptional mechanism that has not previously been demonstrated in differentiating cells, viz. nucleo-cytoplasmic transport of mRNA.

Cell Differentiation↗
PubMed1995

A family of transcripts encoding water channel proteins: tissue-specific expression in the common ice plant.

Seawater-strength salt stress of the ice plant (Mesembryanthemum crystallinum) initially results in wilting, but full turgor is restored within approximately 2 days. We are interested in a mechanistic explanation for this behavior and, as a requisite for in-depth biochemical studies, have begun to analyze gene expression changes in roots coincident with the onset of stress. cDNAs that suggested changes in mRNA amount under stress were found; their deduced amino acid sequences share homologies with proteins of the Mip (major intrinsic protein) gene family and potentially encode aquaporins. One transcript, MipB, was found only in root RNA, whereas two other transcripts, MipA and MipC, were detected in roots and leaves. Transcript levels of MipB were of low abundance. All transcripts declined initially during salt stress but later recovered to at least prestress level. The most drastic decline was in MipA and MipC transcripts. MipA mRNA distribution in roots detected by in situ hybridization indicated that the transcript was present in all cells in the root tip. In the expansion zone of the root where vascular bundles differentiate, MipA transcript amounts were most abundant in the endodermis. In older roots, which had undergone secondary growth, MipA was highly expressed in cell layers surrounding individual xylem strands. MipA was also localized in leaf vascular tissue and, in lower amounts, in mesophyll cells. Transcripts for MipB seemed to be present exclusively in the tip of the root, in a zone before and possibly coincident with the development of a vascular system. MipA- and MipB-encoded proteins expressed in Xenopus oocytes led to increased water permeability. mRNA fluctuations of the most highly expressed MipA and MipC coincided with turgor changes in leaves under stress. As the leaves regained turgor, transcript levels of these water channel proteins increased.

Amino Acid Sequence↗
PubMed1992

Genes encoding the phycobilisome rod substructure are clustered on the Anabaena chromosome: characterization of the phycoerythrocyanin operon.

The phycoerythrocyanin (pec) operon, cloned from Anabaena sp. strain PCC 7120, encodes four genes, pecBACE, located upstream of the C-phycocyanin (cpc) operon. This pec-cpc cluster includes all the genes for the structural components of the phycobilisome rod. Oligonucleotide probes based on the amino-terminal sequence of the phycoerythrocyanin beta subunit were used to clone an 8.0-kbp EcoRI fragment which was determined, by sequencing, to partially overlap the previously cloned cpc operon. A 5.0-kbp EcoRI-ClaI fragment corresponding to the region upstream of the cpc operon was subsequently subcloned and sequenced. Five open reading frames whose polarity of transcription is parallel to that of the cpc genes were identified. pecB and pecA encode the beta and alpha subunits of phycoerythrocyanin, respectively. pecC encodes the phycoerythrocyanin-associated linker polypeptide LR34.5,PEC. The identities of these genes are confirmed by agreement with amino-terminal sequences determined from purified phycobilisome components. A gene homologous to cpcE, found downstream of pecC, has been designated pecE. The cpcE gene product is involved in the attachment of the phycocyanobilin chromophore to the alpha subunit of phycocyanin. Three transcripts were observed by Northern (RNA) analyses. The most abundant of these transcripts, 1.35 kbp, corresponds to the beta and alpha subunit genes, whereas the less-abundant transcripts, 2.3 and 3.1 kbp, correspond to pecBAC and pecBACE, respectively. Phycoerythrocyanin is strongly induced in cells cultured under low light. In parallel, all three transcripts were present at much higher levels in cells cultured under low light.

Amino Acid Sequence↗
PubMed2004

A comparative expression analysis of gene transcripts in post-fertilization developmental stages of bovine embryos produced in vitro or in vivo.

This study was carried out to examine the temporal variation in the relative abundance of transcripts during the post-fertilization stages of bovine embryos derived from in vitro or in vivo culture. For this purpose, cumulus-oocyte complexes obtained from ovaries from slaughterhouses were matured, fertilized and cultured in vitro. The in vitro culture was carried out using CR1 medium. In vivo embryos were derived from superovulated and artificially inseminated Simmental heifers and cows. Embryos were recovered from both systems approximately at day 1 (two-cell), day 2 (four-cell), day 3 (eight-cell), day 4 (16-cell), day 5 (morula) and day 7 (blastocyst) after insemination. Relative abundance of target transcripts was performed using real-time PCR. The transcripts studied were the nucleosome assembly protein, mRNA for alivin 1, Pleckstrin homology Sec7 coiled domain, polyadenylate binding protein, NADH dehydrogenase subunit 2, high-mobility group transcription factor, cytokine-like nuclear factor, NY-REN-58 antigen mRNA, mRNA for KIAA1764 and one novel transcript. These transcripts were derived from our previous study conducted using mRNA differential display reverse transcription-polymerase chain reaction (DDRT-PCR) between in vitro-produced bovine eight-, 16-cell, morula and blastocyst-stage embryos. The results of the present study have demonstrated the temporal variation in the relative abundance of these transcripts between in vitro and in vivo culture systems. Such variation in the relative abundance of transcripts during the post-fertilization developmental stages of in vitro and in vivo embryos may reflect the effect of the in vitro culture condition on the transcriptional activity thereby on the developmental competence of the resulting embryos.

Animals↗
PubMed1991

Modulation by oxygen of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase gene in rat hepatocyte cultures.

In liver phosphoenolpyruvate carboxykinase (PCK) activity, protein and mRNA are localized predominantly in the periportal zone. The activation of the PCK gene by glucagon was studied in primary rat hepatocyte cultures under physiological arterial and venous oxygen tensions [16% and 8% (by vol.)]. PCK gene expression was monitored on the level of transcription, mRNA abundance and enzyme activity as well as enzyme synthesis and degradation. 1. Transcription of the PCK gene was increased by 10 nM glucagon maximally after 0.5 h; it reached nearly basal levels again after 2 h. The increase in transcription was 45% lower under 8% oxygen than under 16% oxygen. 2. PCK mRNA was maximally increased after 2 h under 16% oxygen and after 4 h under 8% oxygen; it subsequently declined to twice the basal values after 8 h. The maximal increase after 2 h was 50% lower under 8% oxygen than under 16% oxygen. 3. PCK enzyme activity was maximally increased after 4-6 h. The maximal enhancement after 4 h was 50% lower under 8% oxygen than under 16% oxygen. 4. The increase in PCK enzyme activity was due to an enhanced synthesis rate of PCK protein. The rate increased after 3 h was 35% lower under 8% oxygen than under 16% oxygen. 5. The degradation of PCK protein was equal under both oxygen tensions. The results show that in cultured rat hepatocytes the induction of PCK gene expression is modulated by physiological concentrations of oxygen. The modulation occurred at the level of gene transcription, mRNA abundance, enzyme protein synthesis and enzyme activity. The periportal to perivenous oxygen gradient could be the major factor responsible for the predominant expression of the PCK gene in the periportal zone.

Animals↗
PubMed1993

Intranuclear foci containing low abundance herpes simplex virus latency-associated transcripts visualized by non-isotopic in situ hybridization.

During latent infection of neurons with herpes simplex virus type 1 (HSV-1), several RNA transcripts of varying abundance arise from a single locus within the virus repeats. The functions of latency-associated transcripts (LATs) are unknown and the relationship between the various RNA species requires further clarification. Reported here is a novel approach to the study of HSV transcripts during latency, based on the increasing realization that cellular and viral RNAs are synthesized and processed by macromolecular complexes that occupy discrete compartments within the nucleoplasm of a cell. High resolution non-isotopic in situ hybridization was used to study the intranuclear topology of HSV-1 LATs in primary sensory neurons of latently infected mice and humans. Low abundance (minor) LATs were localized to sharply defined intranuclear foci of 1 to 3 microns in diameter. On average, there were 2.6 to 2.8 foci/LAT+ neuronal profile (5 microns), representing 13 to 14 foci/cell. In contrast to the focal deployment of minor LATs, the more abundant latency-associated RNAs were distributed diffusely throughout the nucleoplasms of latency infected neurons, with prominent sparing of nucleolar regions. These data establish a foundation for studying the synthesis, processing and transport of LATs in vivo. It should now be possible to investigate the nature of those cellular products which associate with HSV-1 encoded LATs in vivo and thereby determine whether minor LATs are associated with previously characterized macromolecular complexes, such as those responsible for processing of pre-messenger RNA.

Animals↗
PubMed1987

Extensive mitochondrial specific transcription of the Brassica campestris mitochondrial genome.

We constructed a complete transcriptional map of the 218 kb Brassica campestris (turnip) mitochondrial genome. Twenty-four abundant and positionally distinct transcripts larger than 500 nucleotides were identified by Northern analyses. Approximately 30% (61 kb) of the genome is highly transcribed. In addition, a number of less abundant transcripts, many of which overlap with each other and with the major transcripts, were also detected. If each abundant transcript represents a distinct rRNA or protein species, then plant mitochondria would appear to encode a significantly larger number of proteins than do animal mitochondria. Although B. campestris mitochondrial DNA contains a number of chloroplast DNA-derived sequences, none of these chloroplast sequences appear to be transcribed within the mitochondrion. We determined the positions of 12 genes in the B. campestris mitochondrial genome. The order of these genes in B. campestris is completely different than in maize (1) and spinach (2).

Brassica↗
PubMed1995

The human Y chromosome homologue of XG: transcription of a naturally truncated gene.

The XG blood group gene spans PABX1, the pseudoautosomal boundary on the X chromosome. The first three exons are pseudoautosomal and the remaining seven are X-specific. On the Y chromosome SRY and RPS4Y are located in Y-specific sequences within 70 kb of the boundary. Transcription from the XG promoter on the Y chromosome has been detected by cDNA cloning and PCR-based methods. Splicing of the pseudoautosomal exon 3 of XG occurs to multiple sites in Y-specific sequences. Transcripts detected include antisense SRY sequences and XG approximately RPS4Y hybrid transcripts. The heterogeneity and low abundance of transcripts as well as the lack of maintenance of the XG open reading frame in all but one transcript argue against a specific Y-chromosome gene product. An expressed pseudogene of XG, XGPY, has been mapped to interval Yq11.21. XGPY is transcribed and subject to alternative splicing. Sequence comparison suggests that XGPY originated from XG by a gene duplication event in the primate lineage.

Alternative Splicing↗
PubMed2000

Episomal segregation of the adenovirus enhancer sequence by conditional genome rearrangement abrogates late viral gene expression.

We have constructed a recombinant adenovirus gene delivery system that is capable of undergoing growth phase-dependent site-specific recombination. When propagated in 293 producer cells, the vector retains its linear double-stranded form and can be propagated to high titer and purified by conventional procedures. Upon introduction into target cells, the viral chromosome undergoes cyclization to generate an autonomously replicating circular episome and a detached linear fragment. The viral enhancer and reporter gene segregate with the circular episome, which contains no adenovirus open reading frames. The effect of rearrangement of adenovirus gene expression was assessed by quantitative reverse transcription-PCR measurement of the abundance of transcripts encoding the tripartite leader sequence (TPL) of the major late promoter. Whereas nonrearranging viruses produced approximately 10(4) TPL transcripts per 10(6) infecting genomes in the HepG2 liver cell line, no transcripts were detectable in the same cells infected with comparable levels of circularizing vector. Because no helper virus is required to propagate these vectors, the problems of recombination with and contamination by helper virus are eliminated. We also present an efficient and reliable method for generating recombinant adenoviruses.

Adenoviridae↗
PubMed2005

The locus encompassing the latency-associated transcript of herpes simplex virus type 1 interferes with and delays interferon expression in productively infected neuroblastoma cells and trigeminal Ganglia of acutely infected mice.

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) is the only abundant viral transcript expressed in latently infected neurons. LAT inhibits apoptosis, suggesting that it regulates latency by promoting the survival of infected neurons. The LAT locus also contains a newly described gene (AL), which is antisense to LAT and partially overlaps LAT encoding sequences. When human (SK-N-SH) or mouse (neuro-2A) neuroblastoma cells were infected with a virus that does not express LAT or AL gene products (dLAT2903), beta interferon (IFN-beta) and IFN-alpha RNA expression was detected earlier relative to the same cells infected with HSV-1 strains that express LAT and AL. Infection of neuro-2A cells with dLAT2903 also led to higher levels of IFN-beta promoter activity than in cells infected with wild-type (wt) HSV-1. In contrast, IFN RNA expression was the same when human lung fibroblasts were infected with dLAT2903 or wt HSV-1. When BALB/c mice were infected with dLAT2903, IFN-alpha and IFN-beta RNA expression was readily detected in trigeminal ganglia (TG) 4 days after infection. These transcripts were not detected in TG of mice infected with wt HSV-1 or dLAT2903R (marker-rescued dLAT2903) until 6 days postinfection. When TG single-cell suspensions from infected BALB/c mice were prepared and incubated in vitro with wt HSV-1 as a source of antigen, TG cultures prepared from mice infected with dLAT2903 produced and secreted higher levels of IFN protein than wt HSV-1 or dLAT2903R. Collectively, these studies suggest that the LAT locus interferes with and delays IFN expression.

Animals↗
PubMed2006

Varicella zoster virus: out of Africa and into the research laboratory.

This review updates on numerous topics relating to the evolutionary origins of varicella zoster virus (VZV), the replication cycle, virion assembly and the recent genomic analyses. VZV is one of eight human herpesviruses that have existed for at least 400 million years. It has co-evolved with humankind and is present in all nationalities globally. The pathogenesis of varicella (chickenpox) is dependent on viral replication and dispersion through the body in T-lymphocytes. VZV replication is similar to that of herpes simplex virus. A complete analysis of VZV transcripts has identified their relative abundance, with transcripts for the regulatory proteins (open reading frame) ORF62 and ORF63 among the greatest. Studies of virion assembly have shown that endocytosis pathways are involved in the envelopment process by the viral glycoproteins. The complete sequencing of five VZV strains has identified numerous single nucleotide polymorphisms, and in turn, VZV strains have been segregated into European/North American and Asian clades. Furthermore, a small number of mutant VZV strains have been identified. These results suggest more diversity between VZV strains than previously recognized.

Animals↗
PubMed2003

Fxyd3 and Lgi4 expression in the adult mouse: a case of endogenous antisense expression.

We have investigated the expression of Fxyd3 and Lgi4 in the adult mouse by Northern blot analyses and in situ hybridization. Murine Fxyd3 and Lgi4 have been mapped to the same locus on mouse Chromosome (Chr) 7, where the last exon of Fxyd3 completely overlaps with the 3'UTR in the last exon of Lgi4, which is transcribed in the opposite orientation. The Fxyd3 gene (formerly called Mat-8) encodes an 8-kDa transmembrane protein that is upregulated in mammary tumors and can induce a chloride conductance upon RNA injection into Xenopus oocytes. Fxyd3 is a member of the Fxyd family of which several members are tissue-specific regulators of ion channels. Murine Lgi4 is a recently described member of the leucine-rich-repeat gene family Lgi. Northern blot analyses demonstrated a 0.6-kb Fxyd3 transcript with abundant expression in the murine skin, colon, and mammary gland, but low level expression in the brain. In contrast, a 3.2-kb Lgi4 transcript was abundant in brain, with lower level expression in colon. Lgi4 transcription in the skin was detectable only by RT-PCR. A Fxyd3-specific sense cRNA probe hybridized to a transcript in Northern blots of brain and colon RNA that co-migrated with the Lgi4 mRNA. In situ hybridization experiments revealed that both Fxyd3 and Lgi4 were expressed in the same tissue compartments in skin, uterus, intestine, mammary gland, and brain. These results demonstrate that Fxyd3 and Lgi4 transcripts potentially form double-stranded RNA molecules in many cell types in vivo, which may impact on their respective expression.

3' Untranslated Regions↗
PubMed1996

Coordination of protein and mRNA abundances of stromal enzymes and mRNA abundances of the Clp protease subunits during senescence of Phaseolus vulgaris (L.) leaves.

Our objective was to determine the coordination of transcript and/or protein abundances of stromal enzymes during leaf senescence. First trifolioliate leaves of Phaseolus vulgaris L. plants were sampled beginning at the time of full leaf expansion; at this same time, half of the plants were switched to a nutrient solution lacking N. Total RNA and soluble protein abundances decreased after full leaf expansion whereas chlorophyll abundance remained constant; N stress enhanced the decline in these traits. Abundances of ribulose-1,5-bisposphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39), Rubisco activase and phosphoribulokinase (Ru5P kinase; EC 2.7.1.19) decreased after full leaf expansion in a coordinated manner for both treatments. In contrast, adenosine diphosphate glucose (ADPGlc) pyrophosphorylase (EC 2.7.7.27) abundance was relatively constant during natural senescence but did decline similar to the other enzymes under N stress. Northern analyses indicated that transcript abundances for all enzymes declined markedly on a fresh-weight basis just after full leaf expansion. This rapid decline was particularly strong for the Rubisco small subunit (rbcS) transcript. The decline was enhanced by N stress for rbcS and Rubisco activase (rca), but not for Ru5P kinase (prk) and ADPGlc pyrophosphorylase (agp). Transcripts of the Clp protease subunits clpC and clpP declined in abundance just after full leaf expansion, similar to the other mRNA species. When Northern blots were analyzed using equal RNA loads, rbcS transcripts still declined markedly just after full leaf expansion whereas rca and clpC transcripts increased over time. The results indicated that senescence was initiated near the time of full leaf expansion, was accelerated by N stress, and was characterized by large decline in transcripts of stromal enzymes. The decreased mRNA abundances were in general associated with steadily declining stromal protein abundances, with ADPGlc pyrophosphorylase being the notable exception. Transcript analyses for the Clp subunits supported a recent report (Shanklin et al., 1995, Plant Cell 7: 1713-1722) indicating that the Clp protease subunits were constitutive throughout development and suggested that ClpC and ClpP do not function as a senescence-specific proteolytic system in Phaseolus.

Adenosine Triphosphatases↗
PubMed1990

Analysis of the mouse Dhfr/Rep-3 major promoter region by using linker-scanning and internal deletion mutations and DNase I footprinting.

The mouse dihydrofolate reductase (Dhfr) promoter region is buried within a CpG island (a region rich in unmethylated CpG dinucleotides), has a high G+C content, and lacks CAAT and TATA elements. The region contains four 48-bp repeats, each of which contains an Sp1-binding site. Another gene, Rep-3 (formerly designated Rep-1), shares the same general promoter region with Dhfr, being transcribed in the direction opposite that of Dhfr. Both genes appear to be housekeeping genes and are expressed at relatively low levels in all tissues. The 5' termini of the major Dhfr transcripts are separated from the 5' termini of the Rep-3 transcripts by approximately 140 bp. This curious structural arrangement suggested that the two genes might share common regulatory elements. To investigate the promoter sequences driving bidirectional transcription, a series of promoter mutations was constructed. These mutations were assayed by a replicating minigene system and by promoter fusions to the chloramphenicol acetyltransferase gene. Linker-scanning mutations that spanned the four repeats produced a variety of mRNA transcript phenotypes. The effects were primarily quantitative, generally reducing the abundance of transcripts for one or both genes. Some mutations affected Dhfr in a qualitative manner, such as by changing the startpoint of one of the major Dhfr transcripts or changing the relative abundance of the two major Dhfr transcripts. Additionally, protein transcription factors that bind to sequences in the mouse Dhfr/Rep-3 major promoter region, potentially affecting expression of either or both genes, were investigated by DNase I footprinting. The results indicate that multiple protein-DNA interactions occur in this region, reflecting potentially complex transcriptional control mechanisms that might modulate expression of either or both genes under different physiological conditions.

Animals↗
PubMed2005

The Ruminococcus albus pilA1-pilA2 locus: expression and putative role of two adjacent pil genes in pilus formation and bacterial adhesion to cellulose.

Ruminococcus albus produces fimbria-like structures that are involved with the bacterium's adhesion to cellulose. The subunit protein has been identified in strain 8 (CbpC) and strain 20 (GP25) and both are type IV fimbrial (Pil) proteins. The presence of a pil locus that is organized similarly in both strains is reported here together with the results of an initial examination of a second Pil protein. Downstream of the cbpC/gp25 gene (hereafter referred to as pilA1) is a second pilin gene (pilA2). Northern blot analysis of pilA1 and pilA2 transcripts showed that the pilA1 transcript is much more abundant in R. albus 8, and real-time PCR was used to measure pilA1 and pilA2 transcript abundance in R. albus 20 and its adhesion-defective mutant D5. Similar to the findings with R. albus 8, the relative expression of pilA1 in the wild-type strain was 73-fold higher than that of pilA2 following growth with cellobiose, and there were only slight differences between the wild-type and mutant strain in pilA1 and pilA2 transcript abundances, indicating that neither pilA1 nor pilA2 transcription is adversely affected in the mutant strain. Western immunoblots showed that the PilA2 protein is localized primarily to the membrane fraction, and the anti-PilA2 antiserum does not inhibit bacterial adhesion to cellulose. These results suggest that the PilA2 protein plays a role in the synthesis and assembly of type IV fimbriae-like structures by R. albus, but its role is restricted to cell-associated functions, rather than as part of the externalized fimbrial structure.

Amino Acid Sequence↗
PubMed2003

Dynamic regulation of alternative ATP-binding cassette transporter A1 transcripts.

The ATP-binding cassette transporter A1 (ABCA1) gene, a major regulator of high-density lipoprotein (HDL) metabolism, utilizes several transcriptional start sites. The pattern of transcripts among tissues and cells differed significantly. The longest (class 1) transcripts were abundant in adult brain and fetal tissues. Class 2 transcripts predominated in most other tissues. The shortest (class 3) transcripts were present mainly in adult liver and lung. To study the biochemical significance of changes in transcript distribution, two cell models were compared. In primary human fibroblasts, upregulation of mRNA levels by oxysterols and retinoic acid increased the relative proportion of class 2 transcript compared to class 1. Phorbol ester stimulated human macrophage-derived THP-1 cells increased the abundance of class 1 transcripts relative to class 2. In both cell lines class 3 transcript levels were minimal and unchanged. It is shown here for the first time that the regulation of ABCA1 mRNA levels exploits the use of alternative transcription start sites.

ATP Binding Cassette Transporter 1↗