Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “exon 2”

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 37 records · Page 2Linked to original sources
PubMed2002

[Deletion of P16 gene exon 2 in bronchofibroscopic brush-off cells of human lung carcinoma]

OBJECTIVE: To analyze the relationship between deletion of P16 gene exon 2 and lung cancer and to evaluate the possibility of detecting P16 gene exon 2 deletion in brush-off cell instead of resected lung cancer mass. METHODS: P16 gene exon 2 deletion in bronchofibroscopic brush-off cells of lesion side and corresponding normal side was detected through PCR-electrophoresis-Image. Image value of P16 Vs beta-actin <0.6 was considered as P16 gene exon 2 deletion. RESULTS: The rate of P16 gene exon 2 deletion in normal side was 0 (0/19), whereas in lesion side was 35.5%(11/31), there is a significant statistical difference (P<0.01). In SCLC (small -cell lung carcinoma) samples, the rate of P16 gene exon 2 deletion was 0(0/7). whereas in NSCLC (non-small cell lung carcinoma) samples, that was 50%(11/12)(P<0.05). CONCLUSION: P16 gene exon 2 deletion might be related to the oncogenesis and development of lung carcinoma, especially NSCLC. Brush-off cell specimens may replace surgical specimens in Detecting P16 gene exon 2 deletion.

Journal Article↗
PubMed1996

Exon 2-mediated c-myc mRNA decay in vivo is independent of its translation.

We have previously shown that the steady-state level of c-myc mRNA in vivo is primarily controlled by posttranscriptional regulatory mechanisms. To identify the sequences involved in this process, we constructed a series of H-2/myc transgenic lines in which various regions of the human c-MYC gene were placed under the control of the quasi-ubiquitous H-2K class I regulatory sequences. We demonstrated that the presence of one of the two coding exons, exon 2 or exon 3, is sufficient to confer a level of expression of transgene mRNA similar to that of endogenous c-myc in various adult tissues as well as after partial hepatectomy or after protein synthesis inhibition. We now focus on the molecular mechanisms involved in modulation of expression of mRNAs containing c-myc exon 2 sequences, with special emphasis on the coupling between translation and c-myc mRNA turnover. We have undertaken an analysis of expression, both at the mRNA level and at the protein level, of new transgenic constructs in which the translation is impaired either by disruption of the initiation codon or by addition of stop codons upstream of exon 2. Our results show that the translation of c-myc exon 2 is not required for regulated expression of the transgene in the different situations analyzed, and therefore they indicate that the mRNA destabilizing function of exon 2 is independent of translation by ribosomes. Our investigations also reveal that, in the thymus, some H-2/myc transgenes express high levels of mRNA but low levels of protein. Besides the fact that these results suggest the existence of tissue-specific mechanisms that control c-myc translatability in vivo, they also bring another indication of the uncoupling of c-myc mRNA translation and degradation.

Animals↗
PubMed1994

Experimental allergic encephalomyelitis induced by the peptide encoded by exon 2 of the MBP gene, a peptide implicated in remyelination.

The discovery of T lymphocytes reactive to the peptide encoded by exon 2 of the myelin basic protein (MBP) gene in multiple sclerosis (MS) patients has drawn attention to MBP isoforms harboring that peptide as candidate autoantigens. Previously, immunological studies in MS had almost exclusively used the more abundant 18.5 kDa isoform of MBP, which does not contain the exon 2 peptide. Investigations of experimental allergic encephalomyelitis (EAE) have also focussed on the 18.5 kDa MBP isoform and its peptides. Since EAE is an animal model widely used to study MS, we examined the encephalitogenic potential of exon 2 peptide in the SJL/J mouse. Evidence for increased expression of exon 2-containing isoforms during remyelination in mouse CNS suggested that exon 2-sensitized T cells, with encephalitogenic capacity, might be important in the perpetuation of relapsing EAE (rEAE). Our experiments have demonstrated that exon 2 peptide is inherently immunogenic in SJL mice and that EAE could be induced by the adoptive transfer of exon 2-sensitized lymphocytes. Furthermore, the disease could be accentuated by the transfer of short-term exon 2-reactive lines or by a combination of adoptive transfer and antigenic challenge with exon 2 peptide. The immunodominant epitope(s) appeared to localize to the segment bordered by amino acids 59-85.

Amino Acid Sequence↗
PubMed2003

Modulation of the membrane-binding domain of tau protein: splicing regulation of exon 2.

Tau is a microtubule-associated protein whose transcript undergoes complex regulated splicing in the mammalian nervous system. The N-terminal domain of the protein interacts with the axonal membrane, and is modulated by regulated inclusion of exons 2 and 3. These two tau exons are alternatively spliced cassettes, in which exon 3 never appears independently of exon 2. Previous work with tau minigene constructs indicated that exon 2 resembles a constitutive exon. In this study, we show that exon 2 is regulated by a combination of exonic and intronic enhancers and silencers. Furthermore, we demonstrate that known splicing regulators affect the ratio of exon 2 isoforms. Lastly, we tentatively pinpoint the site of action of several splicing factors which regulate tau exon 2.

Amino Acid Sequence↗
PubMed2005

Tau exons 2 and 10, which are misregulated in neurodegenerative diseases, are partly regulated by silencers which bind a SRp30c.SRp55 complex that either recruits or antagonizes htra2beta1.

Tau is a microtubule-associated protein whose transcript undergoes complex regulated splicing in the mammalian nervous system. Exon 2 modulates the tau N-terminal domain, which interacts with the axonal membrane. Exon 10 codes for a microtubule binding domain, increasing the affinity of tau for microtubules. Both exons are excluded from fetal brain, but their default behavior is inclusion, suggesting that silencers are involved in their regulation. Exon 2 is significantly reduced in myotonic dystrophy type 1, whose symptoms include dementia. Mutations that affect exon 10 splicing cause frontotemporal dementia (FTDP). In this study, we investigated three regulators of exon 2 and 10 splicing: serine/arginine-rich (SR) proteins SRp55, SRp30c, and htra2beta1. The first two inhibit both exons; htra2beta1 inhibits exon 2 but activates exon 10. By deletion analysis, we identified splicing silencers located at the 5' end of each exon. Furthermore, we demonstrated that SRp30c and SRp55 bind to both silencers and to each other. In exon 2, htra2beta1 binds to the inhibitory heterodimer through its RS1 domain but not to exon 2, whereas in exon 10 the heterodimer may sterically interfere with htra2beta1 binding to a purine-rich enhancer (defined by FTDP mutation E10-Delta5 = Delta280K) directly downstream of the silencer. Increased exon 10 inclusion in FTDP mutant ENH (N279K) may arise from abolishing SRp30c binding. Also, htra2beta3, a naturally occurring variant of htra2beta1, no longer inhibits exon 2 splicing but can partially rescue splicing of exon 10 in FTDP mutation E10-Delta5. This work provides interesting insights into the splicing regulation of the tau gene.

Animals↗
PubMed2000

Exon-skipping in BCR/ABL is induced by ABL exon 2.

The BCR/ABL fusion gene is pathognomonic for chronic myelogenous leukaemia (CML). We have previously reported alternative splicing of BCR/ABL, as indicated by the detection of both p190- and p210-encoding transcripts, in about 60% of CML patient samples. These exon-skipping events involved the joining of ABL exon 2 to variable upstream BCR exons. Similarly, ABL exon 2 is alternatively spliced to either of two upstream ABL exons (1a or 1b) in c-ABL. We have constructed BCR and BCR/ABL minigenes to study this phenomenon in more detail. These constructs were transfected into various cell types and splicing was assessed by reverse transcriptase PCR. Whereas the basic BCR minigene expressed exon-inclusive transcripts only, insertion of genomic DNA spanning ABL exon 2 induced exon-skipping but only when expressed in the CML cell lines K562 and EM3. In this study we localized the required sequence element to ABL exon 2 itself. These results mimic the splicing phenotype displayed by most CML patients. We propose a model where a trans-factor present in some CML cells interacts with ABL exon 2 pre-mRNA to promote skipping of upstream BCR exons.

Alleles↗
PubMed2006

TGF-β1 regulation of human AT1 receptor mRNA splice variants harboring exon 2.

At least four alternatively spliced mRNAs can be synthesized from the human AT(1)R (hAT(1)R) gene that differ only in the inclusion or exclusion of exon 2 and/or 3. RT-PCR experiments demonstrate that splice variants harboring exon 2 accounts for at least 30% of all the hAT(1)R mRNA transcripts expressed in the human tissues investigated. Since exon 2 contains two upstream AUGs or open reading frames (uORFs), we hypothesized that these AUGs would inhibit the translation of the downstream hAT(1)R protein ORF harbored in exon 4. This study demonstrates that the inclusion of exon 2 in hAT(1)R mRNA transcripts dramatically reduces hAT(1)R protein levels (nine-fold) and significantly attenuates Ang II responsiveness ( approximately four-fold). Interestingly, only when both AUGs were mutated in combination were the hAT(1)R density and Ang II signaling levels comparable with those values obtained using mRNA splice variants that did not include exon 2. This observation is consistent with a model where the majority of the ribosomes likely translate uORF#1 and are then unable to reinitiate at the downstream hAT(1)R ORF, in part due to the presence of AUG#2 and to the short intercistronic spacing. Importantly, TGF-beta(1) treatment (4ng/ml for 4h) of fibroblasts up-regulated hAT(1)R mRNA splice variants, which harbored exon 2, six-fold. Since AT(1)R activation is closely associated with cardiovascular disease, the inclusion of exon 2 by alternative splicing represents a novel mechanism to reduce the overall production of the hAT(1)R protein and possibly limit the potential pathological effects of AT(1)R activation.

Alternative Splicing↗
PubMed2005

Genetic variation within exon 2 of the MHC B-LB // gene in Tibetan chicken.

Genetic variation within exon 2 of chicken major histocompatibility complex B-LB // genes was investigated by PCR amplification, cloning and sequencing of a 374 bp fragment of the indigenous Tibetan chicken genomic DNA. Fifteen novel B-LB // alleles were found. Alignment and comparison of 18 allelic sequences from the individuals sampled revealed a total of 62 variable sites (total of 80 mutations) in exon 2, of which 41 were parsimony informative sites. The nucleotide diversity (pi) within the sequence of exon 2 was calculated to be 0.0718. Analysis of nucleotide variation confirmed a lower level of divergence (0.056 +/- 0.008) as estimated by average pairwise distance within the Tibetan chicken population than the five exotic breeds detected. The relative frequencies of synonymous and non-synonymous nucleotide substitutions within the region were 3.25 +/- 0.94% and 15.61 +/- 2.69% , respectively. These results indicated that the genetic variation within exon 2 seemed to have arisen largely by gene recombination and balancing selection. Alignment of the deduced amino acid sequences of beta1 domain coded by exon 2 revealed 11 synonymous mutations and 27 non-synonymous substitutions at the 38 separate sites. Fifty percent (12/24) of the proposed peptide-binding sites were variable within beta1 domain of chicken MHC B-LB // molecules, of which 11 were unique non-synonymous amino acid substitutions. These particular non-synonymous substitutions are considered to be associated with immunological specificity of MHC B-LB // molecule in Tibetan chicken, and they can provide a molecular biological basis for the study of disease resistance in chicken.

Animals↗
PubMed2003

Lack of mu-opioid receptor-mediated G-protein activation in the spinal cord of mice lacking Exon 1 or Exons 2 and 3 of the MOR-1 gene.

The G-protein activation induced by mu-opioid receptor agonists was determined in spinal cord membranes from two types of mu-opioid receptor knockout mice: mice with a disruption of exon 1 (MOR (Exon 1)-KO) or exons 2 and 3 (MOR (Exons 2 and 3)-KO) of the mu-opioid receptor gene. The G-protein activation induced by the opioid agonists was measured by monitoring the increases of guanosine-5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTP gamma S) binding. The mu-opioid receptor agonists (D-Ala(2),N-MePhe (4),Gly-ol(5)]enkephalin, endomorphin-1, endomorphin-2, morphine, morphine-6 beta-glucuronide, and fentanyl produced concentration-dependent increases of [(35)S]GTP gamma S binding to spinal cord membranes in wild-type mice, but not in MOR (Exon 1)-KO mice or MOR (Exons 2 and 3)-KO mice. On the other hand, the delta-opioid receptor agonist [D-Pen (2,5)]enkephalin, the kappa-opioid receptor agonist (-)U50,488H, or the ORL1-receptor agonist nociception increased [(35)S]GTP gamma S binding in the spinal cord membranes from both MOR (Exon 1)-KO mice and MOR (Exons 2 and 3)-KO mice to the same extent as in the corresponding wild-type mice. The results provide further information about the important roles of the sequences encoded within exon 1 and exons 2 and 3 of mu-opioid receptor gene for the activation of G-proteins by mu-opioid receptor agonists in the mouse spinal cord.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed2002

Nucleocytoplasmic transfer of the NF2 tumor suppressor protein merlin is regulated by exon 2 and a CRM1-dependent nuclear export signal in exon 15.

The neurofibromatosis 2 protein merlin is a classical tumor suppressor protein. Germline mutations predispose to the development of schwannomas, meningiomas and ependymomas. Merlin has been implicated in cellular migration and adhesion. This function is reflected in its subcellular localization at the plasma membrane and known interacting partners. Merlin has been regarded as an exception in not exerting a functional role within the nucleus as other tumor suppressors do. Here, we show that detection of wild-type protein in the nucleus is a rare event. However, splicing out of exon 2 leads to unrestricted entry into the nucleus. Skipping of adjacent exon 3 has no comparable effect ruling out an unspecific effect due to misfolding of the 4.1/JEF domain. Exon 2 functions as a cytoplasmic retention factor as it is able to confer sole cytoplasmic localization to a GFP fusion protein. Nuclear entry of merlin is thus regulated by alternative splicing within the 4.1/JEF domain and analogous to band 4.1 protein. Merlin's ability to enter the nucleus is complemented by a full nuclear-cytoplasmic shuttle protein with a functional Rev-type nuclear export sequence (NES) within exon 15 that facilitates export via the CRM1/exportin pathway. Deletion of this NES or treatment with the CRM1-specific inhibitor leptomycin B leads to overall nuclear accumulation of merlin isoforms missing exon 2. A cellular function different to the wild-type protein is implied for naturally occurring splice variants lacking exon 2. A putative effect of merlin as a transcriptional regulator and identification of nuclear binding partners remains to be elucidated.

3T3 Cells↗
PubMed1989

50 residues coded by exon 2 of chicken lysozyme carry residual catalytic activity.

The generally accepted hypothesis that exons code for fundamental polypeptide structures was tested with a fusion protein consisting of almost the entire polypeptide coded by exon 2 of chicken lysozyme fused to the N-terminus of beta-galactosidase of E.coli. Exon 2 encodes residues 28-81 of lysozyme. It thus contains Glu 35 and Asp 52, which are essential for hydrolysis of glycosidic bonds. The exon 2-beta-galactosidase fusion protein hydrolysed the substrate 4-methylumbelliferyl-N,N',N''-triacetyl-chitotrioside with a reaction rate about 1/40,000 of that of native lysozyme. The low hydrolysis rate of exon 2-peptide is partially caused by its low affinity to its substrate.

Animals↗
PubMed2005

Restriction fragment length polymorphism of exon 2 Ovar-DRB1 gene in Polish Heath Sheep and Polish Lowland Sheep.

Exon 2 of the Ovar-DR gene is known to encode the MHC outer domain (alpha or beta chain) that forms the binding area to antigens presented. The study was aimed at analysing exon 2 Ovar -DRB1 gene polymorphism in Polish Heath Sheep and Polish Lowland Sheep (Zelazna variety). A total of 101 and 99 ewes of the respective breeds were included in this study. We identified 65 different haplotypes in Polish Heath Sheep and 68 in Polish Lowland Sheep. The PCR-RFLP method and PCR products sequencing made it possible to identify two new sequences of exon 2 Ovar-DRB1 gene (AY230000 and AY248695). A distinct polymorphism in the exon 2 sequence presents possibilities for immune response toward a great variety of pathogens.

Animals↗
PubMed1997

The IGHG3 gene shows a structural polymorphism characterized by different hinge lengths: sequence of a new 2-exon hinge gene.

Four of the five human IGHG genes (G1, GP, G2, and G4) display a hinge region consisting of a unique exon. In contrast, IGHG3 exhibits a different structure in which the hinge is constituted by four or, less frequently, three exons. We report here the nucleotide sequence of a new 2-exon hinge G3 gene found in a Mandenka individual from Eastern Senegal. A comparison of this sequence with that of 4-exon and 3-exon hinge G3 genes suggests that the 3-exon and 2-exon hinge forms arose independently by deletion events in a 4-exon hinge gene.

B-Lymphocytes↗
PubMed1993

Induction of gene expression by exon 2 of the major E1A proteins of adenovirus type 5.

We have constructed an adenovirus type 5 (Ad5) E1A mutant, dl1119/520, that produces essentially only exon 2 of the major E1A proteins. In infected primary baby rat kidney cells, this mutant induced expression of the E1B 55-kDa protein, and in infected human KB cells, it induced expression of this protein, the E2A 72-kDa protein, and hexon. In KB cells, this mutant grew substantially better than Ad5 dl312, which lacks E1A, and as well as Ad5 dl520, an E1A mutant producing only the 243-residue protein. These results suggest that exon 2 of E1A proteins on its own was able to activate gene expression. We also constructed mutants of dl1119/520, containing small deletions in regions of exon 2 that others found to be associated with effects on the properties of E1A transformants. None of these deletions destroyed gene activation completely, indicating that there may be some redundancy among sequences in exon 2 for inducing gene expression. The two deletions that decreased induction the most, residues 224 to 238 and 255 to 270, were in regions reported to be associated with the expression of a metalloprotease and with enhanced transformation, suggesting that exon 2 may regulate expression of genes governing cell growth. It is remarkable that all sections of E1A proteins, exon 1, the unique region, and exon 2, have now been found to affect gene expression.

Adenoviridae↗
PubMed2001

Role of exon 2-encoded beta -domain of the von Hippel-Lindau tumor suppressor protein.

Sporadic clear cell renal carcinomas frequently harbor inactivating mutations in exon 2 of the von Hippel-Lindau (VHL) tumor suppressor gene. Here, we examine the effect of the loss of exon 2-encoded beta-domain function on VHL biochemical properties. Exon 2-encoded residues are required for VHL-mediated NEDD8 conjugation on cullin-2 and assembly with hypoxia-inducible factor alpha (HIFalpha) and fibronectin. These residues are not essential for VHL ability to assemble with elongin BC/cullin-2, to display E3 ubiquitin ligase activity in vitro and to confer energy-dependent nuclear import properties to a reporter protein. Localization studies in HIF-1alpha-null embryonic cells suggest that exon 2-encoded beta-domain mediates transcription-dependent nuclear/cytoplasmic shuttling of VHL independently of assembly with HIF-1alpha and oxygen concentration. Exon 3-encoded alpha-helical domain is required for VHL complex formation with BC/cullin-2 and E3 ubiquitin ligase activity, for binding to HIFalpha/fibronectin, but this domain is not essential for transcription-dependent nuclear/cytoplasmic trafficking. VHL(-/-) renal carcinoma cells expressing beta-domain mutants failed to produce an extracellular fibronectin matrix and to degrade HIFalpha, which accumulated exclusively in the nucleus of normoxic cells. These results demonstrate that exon 2-encoded residues are involved in two independent functions: substrate protein recognition and transcription-dependent nuclear/cytoplasmic trafficking. They also suggest that beta-domain mutations inactivate VHL function differently than alpha-domain mutations, potentially providing an explanation for the relationship between different mutations of the VHL gene and clinical outcome.

Adenoviridae↗
PubMed2002

Loss of mu-opioid receptor-mediated G-protein activation in the pons/medulla of mice lacking the exons 2 and 3 of mu-opioid receptor gene.

The G-protein activation induced by mu-opioid receptor agonists in the pons/medulla membrane obtained from mice lacking exons 2 and 3 of mu-opioid receptor gene (MOR (Exons 2 and 3)-knockout (KO) mice) was investigated by monitoring guanosine-5'-o-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) binding. The MOR agonists D-Ala2,MePhe4,Gly(ol)5)enkephalin, endomorphin-1 and endomorphin-2 each produced concentration-dependent increases in [(35)S]GTPgammaS binding to pons/medulla membrane in wild-type mice, but not in MOR (Exons 2 and 3)-KO mice. beta-Endorphin also produced a concentration-dependent increase of [(35)S]GTPgammaS binding to pons/medulla membrane in wild-type mice, however the increase of [(35)S]GTPgammaS binding induced by beta-endorphin was partially attenuated in MOR (Exons 2 and 3)-KO mice. The present results suggest that MOR that is created from the sequences encoded with exons 2 and 3 of the MOR gene, as has been previously observed in studies of mice lacking exon 1 of this gene, may be another critical target for the activation of G-protein by MOR agonists in the mouse pons/medulla.

Analgesics, Opioid↗
PubMed1998

HLA-C high resolution typing: analysis of exons 2 and 3 by sequence based typing and detection of polymorphisms in exons 1-5 by sequence specific primers.

HLA-C high resolution sequence based typing developed in this study involves a unique DNA amplification encompassing exon 1 to intron 3 and four fluorescent sequencing reactions covering exon 2 and 3. Both dye primer and dye terminator sequencing techniques were performed and results compared. This approach allowed the identification of all of the 50 HLA-C allelic variants so far described, except for two allele pairs that are distinguished by non-coding nucleotide changes (Cw*12021 = 12022, Cw*15051 = 15052) and three allele pairs (Cw*0701 = 706, Cw*1701 = 1702 and Cw*1801 = 1802) that share the same nucleotide sequence in exon 2 and 3. For complete subtyping of these allelic variants, an amplification based on sequence specific primers (PCR-SSP) was used. No ambiguous heterozygous combinations of alleles were detected in our panel so far. HLA-C typing data obtained by this method were compared with data from serological and low resolution PCR-SSP typing, which had been performed previously on the samples sequenced.

Base Sequence↗
PubMed1995

Function of exon 2 in optimal trans-activation by Tat of HIV type 2.

HIV-1 and HIV-2 are human retroviruses whose life cycles require viral regulatory proteins, one of which is the trans-activator, Tat. Tat of HIV-1 (Tat-1) displays modular function with independent activation function localized to the amino-terminal, cysteine-rich, and core regions and independent RNA-binding function localized to a basic region. These functional domains are contained in the first of two exons encoding Tat-1; deletion of exon 2 does not contribute to functional domains of Tat-1. Tat of HIV-2 (Tat-2) has structurally analogous regions, but the amino terminus, basic region, and carboxy terminus encoded by exon 2 display amino acid sequence and functional divergence compared to Tat-1. We have shown that, in contrast to Tat-1, exon 2 of Tat-2 (residues 100 to 130) is required for optimal trans-activation of HIV-1 and HIV-2 long terminal repeats (LTRs). Here we demonstrate that a series of basic residues in exon 2 are required for these effects. Exon 2 does not alter the level of protein expression of Tat-2. Further, in the context of heterologous DNA binding, exon 2 does not contribute to activation function. These data suggest that full-length Tat-2 results in optimal trans-activation through enhanced RNA-binding function of exon 1 by involvement of a basic region in exon 2. Differential expression of short and full-length Tats during different stages of the HIV-2 life cycle might regulate levels of viral expression, viral replication, and resultant cytopathology.

Amino Acid Sequence↗