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Results for “Translational repression”

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PubMed2006

MIWI associates with translational machinery and PIWI-interacting RNAs (piRNAs) in regulating spermatogenesis.

Noncoding small RNAs have emerged as important regulators of gene expression at both transcriptional and posttranscriptional levels. Particularly, microRNA (miRNA)-mediated translational repression involving PIWI/Argonaute family proteins has been widely recognized as a novel mechanism of gene regulation. We previously reported that MIWI, a murine PIWI family member, is required for initiating spermiogenesis, a process that transforms round spermatids into mature sperm. MIWI is a cytoplasmic protein present in spermatocytes and round spermatids, and it is required for the expression of its target mRNAs involved in spermiogenesis. Most recently, we discovered a class of noncoding small RNAs called PIWI-interacting RNAs (piRNAs) that are abundantly expressed during spermiogenesis in a MIWI-dependent fashion. Here, we show that MIWI associates with both piRNAs and mRNAs in cytosolic ribonucleoprotein and polysomal fractions. As polysomes increase in early spermiogenesis, MIWI increases in polysome fractions. Moreover, MIWI associates with the mRNA cap-binding complex. Interestingly, MIWI is required for the expression of not only piRNAs but also a subset of miRNAs, despite the presence of Dicer. These results suggest that MIWI has a complicated role in the biogenesis and/or maintenance of two distinct types of small RNAs. Together, our results indicate that MIWI, a PIWI subfamily protein, uses piRNA as the major, but not exclusive, binding partner, and it is associated with translational machinery.

Animals↗

PubMed2001

Feedback inhibition of the unfolded protein response by GADD34-mediated dephosphorylation of eIF2alpha.

Phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha) on serine 51 integrates general translation repression with activation of stress-inducible genes such as ATF4, CHOP, and BiP in the unfolded protein response. We sought to identify new genes active in this phospho-eIF2alpha-dependent signaling pathway by screening a library of recombinant retroviruses for clones that inhibit the expression of a CHOP::GFP reporter. A retrovirus encoding the COOH terminus of growth arrest and DNA damage gene (GADD)34, also known as MYD116 (Fornace, A.J., D.W. Neibert, M.C. Hollander, J.D. Luethy, M. Papathanasiou, J. Fragoli, and N.J. Holbrook. 1989. Mol. Cell. Biol. 9:4196-4203; Lord K.A., B. Hoffman-Lieberman, and D.A. Lieberman. 1990. Nucleic Acid Res. 18:2823), was isolated and found to attenuate CHOP (also known as GADD153) activation by both protein malfolding in the endoplasmic reticulum, and amino acid deprivation. Despite normal activity of the cognate stress-inducible eIF2alpha kinases PERK (also known as PEK) and GCN2, phospho-eIF2alpha levels were markedly diminished in GADD34-overexpressing cells. GADD34 formed a complex with the catalytic subunit of protein phosphatase 1 (PP1c) that specifically promoted the dephosphorylation of eIF2alpha in vitro. Mutations that interfered with the interaction with PP1c prevented the dephosphorylation of eIF2alpha and blocked attenuation of CHOP by GADD34. Expression of GADD34 is stress dependent, and was absent in PERK(-)/- and GCN2(-)/- cells. These findings implicate GADD34-mediated dephosphorylation of eIF2alpha in a negative feedback loop that inhibits stress-induced gene expression, and that might promote recovery from translational inhibition in the unfolded protein response.

Activating Transcription Factor 4↗

PubMed1985

Regulation of messenger RNA stability in mouse erythroleukemia cells.

The decay rates of several messenger RNA species were determined in mouse erythroleukemia cells. The t1/2 values for the actin and tubulin mRNAs were 16 to 26 hours and about seven hours, respectively. The globin mRNA, and two mRNA species subject to translation repression, the P40 and P21 mRNAs, were about as stable as the ribosomal RNA. A stable tubulin mRNA component also appeared to be present in the cells. Exposure of the cells to dimethylsulfoxide for 48 hours led to considerable increases in the rates of decay of all but the globin mRNA. The induction of erythroid differentiation caused by the drug appears to lead to activation of a mRNA-degradation process that affects individual species to different degrees. The newly synthesized actin and tubulin mRNAs lost their poly(A) rather rapidly. This was accompanied by accumulation of poly(A)-deficient mRNA chains, particularly in the case of actin mRNA. The steady-state distribution of mRNA components, determined by Northern blot analysis, also showed that the actin mRNA and one tubulin mRNA species have a high proportion of poly(A)-deficient molecules. The globin, P40 and P21 mRNAs showed little tendency to lose their poly(A) sequence. The steady-state globin and P40 mRNAs also had a low proportion of chains depleted of poly(A). For all five species, the proportions of poly(A)-deficient chains in newly synthesized mRNA were about the same in uninduced and induced cells, in spite of the large decreases in mRNA stability in the induced cells. The lack of correlation between tendency to lose poly(A) and rate of mRNA decay, and the large accumulation of poly(A)-deficient molecules in the cases of the actin and tubulin mRNAs suggest that the stability of mRNA is not determined solely by the presence of poly(A) on the RNA chains. The behavior of the untranslated species in induced and uninduced cells also fails to support the notion of a relationship between translation and mRNA decay.

Actins↗

PubMed1998

The essential Gcd10p-Gcd14p nuclear complex is required for 1-methyladenosine modification and maturation of initiator methionyl-tRNA.

Gcd10p and Gcd14p are essential proteins required for the initiation of protein synthesis and translational repression of GCN4 mRNA. The phenotypes of gcd10 mutants were suppressed by high-copy-number IMT genes, encoding initiator methionyl tRNA (tRNAiMet), or LHP1, encoding the yeast homolog of the human La autoantigen. The gcd10-504 mutation led to a reduction in steady-state levels of mature tRNAiMet, attributable to increased turnover rather than decreased synthesis of pre-tRNAiMet. Remarkably, the lethality of a GCD10 deletion was suppressed by high-copy-number IMT4, indicating that its role in expression of mature tRNAiMet is the essential function of Gcd10p. A gcd14-2 mutant also showed reduced amounts of mature tRNAiMet, but in addition, displayed a defect in pre-tRNAiMet processing. Gcd10p and Gcd14p were found to be subunits of a protein complex with prominent nuclear localization, suggesting a direct role in tRNAiMet maturation. The chromatographic behavior of elongator and initiator tRNAMet on a RPC-5 column indicated that both species are altered structurally in gcd10Delta cells, and analysis of base modifications revealed that 1-methyladenosine (m1A) is undetectable in gcd10Delta tRNA. Interestingly, gcd10 and gcd14 mutations had no effect on processing or accumulation of elongator tRNAMet, which also contains m1A at position 58, suggesting a unique requirement for this base modification in initiator maturation.

Adenosine↗

PubMed1987

Induction of collagen synthesis by ascorbic acid. A possible mechanism.

L-Ascorbic acid stimulates procollagen synthesis in cultured human skin fibroblasts without appreciably altering noncollagen protein synthesis. The effect is unrelated to intracellular degradation of newly synthesized procollagen. Levels of mRNA for pro alpha 1(I), pro alpha 2(I), and pro alpha 1(III), measured by hybridization with the corresponding cDNA probes, are elevated in the presence of ascorbic acid, whereas the level of mRNA for fibronectin is unchanged. Levels of functional mRNA for procollagen, measured in a cell-free translation assay, are specifically increased in the presence of ascorbic acid. Thus, ascorbic acid appears to control the expression of three different procollagen genes, each of which is located on a separate chromosome. It is proposed that intracellularly accumulated procollagen in ascorbate deficiency may lead to a translational repression of procollagen synthesis. Ascorbic acid may relieve this block by promoting hydroxyproline formation and, consequently, secretion of procollagen from the cell. The increased level of procollagen mRNA under the influence of ascorbic acid may be secondary to increased synthesis of procollagen polypeptides; the control point may be gene transcription or mRNA degradation.

Aging↗

PubMed2026

A Biomimetic Dual-Targeting Nano-APA-Editor Reprograms the 3'UTR Landscape for Tongue Squamous Cell Carcinoma Therapy.

Targeting post-transcriptional dysregulation of tumor suppressors represents a new frontier in cancer therapy. Here, we identify the alternative polyadenylation (APA) regulator NUDT21 as a pivotal therapeutic target in oral squamous cell carcinoma (OSCC). NUDT21 is highly upregulated, correlating strongly with poor survival and advanced clinical stage. We outline a pathogenic mechanism whereby NUDT21 drives this phenotype by forcing a network of tumor suppressor transcripts, notably PTEN, into translationally-repressed, long-3'UTR isoforms. To therapeutically "re-engineer" this APA switch, we design a "Nano-APA-editor." This platform features an HMSN core with an sgRNA-NUDT21 payload and a hierarchical targeting strategy: a cancer-educated dendritic cell (DC) membrane for biomimetic camouflage and homotypic affinity, "gated" by a TA-aptamer for final precision. This system enables potent and selective NUDT21 silencing, driving a shift toward short-3'UTR isoforms. Consequently, the Nano-APA-editor effectively reinstates PTEN and associated suppressors and inhibits multiple malignant phenotypes in vitro. In an orthotopic OSCC model, it demonstrates profound tumor regression, outperforming conventional chemotherapy (PTX) with excellent biocompatibility. In vivo analysis confirmed target engagement (NUDT21-down) and functional restoration (PTEN-, WEE1-, TGF-β-up). This work validates a "post-transcriptional re-engineering" strategy, executed by a logically designed nanoplatform, as a powerful and safe modality for precision gene therapy.

Humans↗

PubMed2005

Molecular mechanisms of RNAi: implications for development and disease.

Research over the past few years has led to dramatic new discoveries on the role of double-stranded RNA (dsRNA) in the cell. RNA duplexes have been shown to orchestrate epigenetic changes, repress translation, and direct mRNA degradation in a sequence-specific manner. These diverse effects of dsRNA on gene expression have been termed RNA interference (RNAi). In addition to playing a role in viral defense and silencing transposons, RNAi also has a critical function in a number of developmental processes in the embryo. In this review, we explore these roles and discuss the molecular mechanisms behind dsRNA-mediated gene silencing. Further, we address the use of RNAi as a tool to study gene function in biology, and as a strategy for treating human disease.

Animals↗

PubMed2006

Computational identification of microRNAs and their targets.

One of the most important advances in biology in recent years may be the discovery of RNAs that can regulate gene expression. As one kind of such functional noncoding RNAs, microRNAs (miRNAs) form a class of endogenous 19-23-nucleotide RNAs that can have important regulatory roles in animals and plants by targeting transcripts for cleavage or translational repression. Since the discovery of the very first miRNAs, computational methods have been an invaluable tool that can complement experimental approaches to understand the biology of miRNAs. Most computational approaches associated with miRNA research can be classified into two broad categories, namely miRNA gene identification and miRNA target prediction. In this review, we summarize the principles of in silico prediction of miRNAs and their targets, and provide a comprehensive survey of specific methods that have been proposed in the field.

Animals↗

PubMed1996

The role of thymidylate synthase as an RNA binding protein.

Thymidylate synthase plays a central role in the biosynthesis of thymidylate, an essential precursor for DNA biosynthesis. In addition to its role in catalysis and cellular metabolism, it is now appreciated that thymidylate synthase functions as an RNA binding protein. Specifically, thymidylate synthase binds with high affinity to its own mRNA, resulting in translational repression. An extensive series of experiments has been performed to elucidate the molecular elements underlying the interaction between thymidylate synthase and its own mRNA. In addition to characterization of the underlying cis- and trans-acting elements, recent studies have shown that thymidylate synthase has the capacity to bind specifically to other cellular RNA species. While the biological significance of these other RNA/thymidylate synthase interactions remains to be defined, this work suggests a potential role for TS in coordinately regulating several critical aspects of cellular metabolism.

Animals↗

PubMed1990

Protein synthesis initiation factor modifications during viral infections: implications for translational control.

Infection of tissue culture cells with certain viruses results in the shutoff of host cell protein synthesis. We have examined virally infected cell lysates using two-dimensional gel electrophoresis and immunoblotting to ascertain whether initiation factor protein modifications are correlated with translational repression. Moderate increases in eukaryotic initiation factor (eIF)-2 alpha phosphorylation are detected in reovirus- and adenovirus-infected cells, as reported previously (Samuel et al., 1984; O'Malley et al., 1989). Neither vesicular stomatitis virus, vaccinia virus, frog virus III, rhinovirus, nor encephalomyocarditis virus caused significantly increased 2 alpha phosphorylation. There were no reproducible, significant changes in eIF-4A, eIF-4B, or eIF-2 beta in cells infected by any of these viruses. The cleavage of eIF-4F subunit p220, such as has been previously demonstrated to occur in poliovirus (Etchison et al., 1982) and rhinovirus (Etchison and Fout, 1985), was not detected in any of the other virus infections analyzed.

Adenoviridae↗

PubMed1995

The proto-oncogene/translation factor eIF4E: a survey of its expression in breast carcinomas.

The eukaryotic translation initiation factor eIF-4E binds to the cap structure of mRNAs as one component of the eIF-4 translation initiation complex, which mediates the recruitment of mRNA to the ribosomes. Overexpression of eIF-4E can result in oncogenic transformation and uncontrolled growth of mammalian cells, presumably by facilitating the expression of growth-control gene products which are normally translationally repressed. Whereas the mechanism of eIF-4E-mediated transformation is being actively pursued, clinical investigations into the expression of eIF-4E in prevalent human cancers are lacking. We have recently initiated a screen of breast carcinomas by probing with eIF-4E antiserum. Using Western blots, we have analyzed the level of eIF-4E in 38 carcinomas, 7 normal samples and 3 fibroadenomas. We found that eIF-4E was elevated 3- to 10-fold in virtually all the carcinomas we analyzed, but not in fibroadenomas. This analysis was also confirmed by immunohistological staining in situ, showing that overexpression of eIF-4E can be readily identified at the single-cell level. Our results suggest that an elevation of eIF-4E may be an essential component in the development of breast cancer.

Adenoma↗

PubMed1995

Requirements for iron-regulated degradation of the RNA binding protein, iron regulatory protein 2.

Iron regulatory proteins (IRPs) regulate the expression of genes involved in iron metabolism whose transcripts contain RNA stem-loop motifs known as iron-responsive elements (IREs). When iron concentrations are low, IRPs bind to IREs in the 5' untranslated region (UTR) of transcripts where they repress translation, or the 3' UTR of transcripts where they inhibit degradation. The RNA binding activities of the homologous proteins IRP1 and IRP2 are both regulated post-translationally. The binding activity of IRP2 is regulated by the degradation of the protein when cells are iron-replete. Here, we demonstrate that a 73 amino acid sequence that corresponds to a unique exon in IRP2 contains a sequence required for rapid degradation in iron-replete cells. The deletion of this sequence eliminates the rapid turnover of IRP2, whereas the transfer of this sequence to the corresponding position in the homologous protein IRP1 confers the capacity for iron-dependent degradation upon IRP1. Site-directed mutagenesis has demonstrated that specific cysteines within the IRP2 exon are required for iron-dependent degradation. The degradation of IRP2 appears to be mediated by the proteasome in iron-replete cells. When degradation is prevented, the RNA binding activity of IRP2 is not regulated by iron concentration. Thus, degradation is required for the regulation of the RNA binding activity of IRP2.

Amino Acid Sequence↗

PubMed2007

MicroRNAs and their regulatory roles in animals and plants.

microRNAs (miRNAs) are an abundant class of newly identified endogenous non-protein-coding small RNAs. They exist in animals, plants, and viruses, and play an important role in gene silencing. Translational repression, mRNA cleavage, and mRNA decay initiated by miRNA-directed deadenylation of targeted mRNAs are three mechanisms of miRNA-guided gene regulation at the post-transcriptional levels. Many miRNAs are highly conserved in animals and plants, suggesting that they play an essential function in plants and animals. Lots of investigations indicate that miRNAs are involved in multiple biological processes, including stem cell differentiation, organ development, phase change, signaling, disease, cancer, and response to biotic and abiotic environmental stresses. This review provides a general background and current advance on the discovery, history, biogenesis, genomics, mechanisms, and functions of miRNAs.

Animals↗

PubMed2003

Gene expression profiling of ciliary neurotrophic factor-overexpressing rat striatal progenitor cells (ST14A) indicates improved stress response during the early stage of differentiation.

Neuronal progenitor cells delivering neurotrophic factors are a promising therapeutic tool for treatment of neurodegenerative diseases. Although several promising results have come from studies in different animal models, detailed knowledge of the action of neurotrophic factors in the CNS is still lacking. A clonally derived, immortalized rat striatal cell line (ST14A) expressing ciliary neurotrophic factor (CNTF) offers a stable and controlled background with which to analyze CNTF actions on the transcriptional level in CNS progenitor cells. To identify early transcriptional changes induced by CNTF expression, we transfected the CNTF gene into ST14A cells, which differentiate at the nonpermissive temperature of 39 degrees C via suppression of the immortalizing SV40 large T antigen. This shows a CNTF-dependent hypoxic/ischemic stress response during the earliest stage of differentiation, with expression of specific transcripts and evidence of translational repression leading to decreased protein synthesis in the transfected cells. This process is mediated by the Ras/MAP kinase pathway and is accompanied by impaired proliferation and metabolism as well as signs of neuronal differentiation. The stress-like response in the early stage of differentiation improves the ability of the transfected cells to respond to and cope with a stressful environment in vivo. The present data indicate higher viability, longer life, and greater differentiation capacity of CNTF-ST14A cells if they are used for transplantation. We conclude that the stress-like response during the early stage of differentiation improves the ability of the CNTF-ST14A cells to respond and adapt to a stressful environment, which renders them useful candidate cells for in vivo trials of treatment for neurodegenerative diseases in animal models, e.g., of Huntington's disease.

Animals↗

PubMed1994

Differential expression of alpha-actin mRNA and immunoreactive protein in brain microvascular pericytes and smooth muscle cells.

Hypertension has been linked to opening of the blood-brain barrier and may be related to the expression of the smooth muscle alpha-actin gene in contractile cells at the brain microvasculature. However, the cellular origin (i.e., endothelial cells, pericytes, smooth muscle cells) of the alpha-actin mRNA in the brain microvasculature is not clearly identified. Therefore, we investigated the abundance of actin mRNA by Northern blot analysis in isolated brain microvessels and in brain microvascular endothelial or pericytes in tissue culture. All samples showed the characteristic 2.1 kb transcript corresponding to cytoplasmic beta and gamma isoform mRNA. The 1.7 kb transcript corresponding to smooth muscle alpha-actin was detected in freshly isolated bovine brain microvessels, in primary cultures of brain microvascular pericytes, or endothelial cells; the latter cultures contain both endothelial cells and pericytes. The alpha-actin mRNA was absent in a cloned bovine brain endothelial cell line. The relative abundance of the alpha/(beta + gamma) actin transcript ratio was: cultured pericytes > freshly isolated microvessels > endothelial primary. The cellular distribution of the smooth muscle alpha-actin immunoreactive protein was studied by immunocytochemistry in cytospun/methanol-fixed isolated bovine brain microvessels with a monoclonal antibody directed to the amino-terminal decapeptide of the smooth muscle alpha-actin isoform. This antibody reacted strongly with precapillary arterioles of isolated microvessels, whereas no immunostaining was observed in either capillary endothelial cells or in pericytes. In conclusion, the alpha-actin mRNA is expressed in brain microvascular pericytes in tissue culture, but the immunoreactive alpha-actin protein is not expressed in brain microvascular pericytes in vivo. These data suggest that either 1) alpha-actin gene expression is induced in capillary pericytes in tissue culture or 2) alpha-actin mRNA in brain capillary pericytes in vivo is subject to translational repression resulting in no detectable alpha-actin protein under normal conditions.

Actins↗

PubMed2004

Expression of eukaryotic initiation factor 4E in gastric adenocarcinoma and its association with clinical outcome.

BACKGROUND AND OBJECTIVES: Overexpression of eIF4E can result in oncogenic transformation and uncontrolled growth of mammalian cells, presumably by facilitating the expression of growth-control gene products, which are normally translationally repressed. Overexpression of eIF4E was present in human breast carcinoma and human head and neck squamous cell carcinoma, and may be of prognostic value in breast carcinomas. In order to elucidate the clinical significance of eIF4E expression, this study was conducted to quantify expression of eIF4E in human gastric cancer tissue and correlate them with clinicopathological factors and patient survival. METHODS: Specimens from sixty-nine patients with gastric adenocarcinoma were analyzed and eIF4E overexpression was quantified by Western blot analysis. Quantification of eIF4E levels in cancer was expressed relative to controls from non-tumorous mucosa of the same patients. Confirmation of eIF4E overexpression at the cellular level was performed using immunohistochemical staining. The association of clinicopathologic factors and survival with eIF4E expression was analyzed. RESULTS: In non-tumorous parts of specimens, overexpression of eIF4E was always present in gastric glands but not in gastric pits lining mucosa, and it was also expressed in the areas of intestinal metaplasia and dysplasia. In the 69 specimens, the mean eIF4E expression was 5.77 +/- 8.55-fold (mean +/- standard deviation), ranged from from 0.1-fold to 38-fold. The degree of eIF4E expression appeared to be independent of invasion depth of tumor, lymph node metastasis, Lauren classification, Borrmann types, and Helicobacter pylori infection. Marked overexpression of eIF4E (more than seven-fold) was correlated with tumor vascular invasion (P = 0.046, Fisher exact-test). The survival rate of the patients with underexpression or mild overexpression of eIF4E (less than sevenfold) was significantly higher than that with marked eIF4E overexpression (more than sevenfold) (P = 0.01734, log rank test). CONCLUSIONS: Marked eIF4E overexpression in gastric cancer was found to be associated with vascular invasion. The prognosis for gastric cancer patients with marked overexpression of eIF4E was worse than those with underexpression. It may serve as an additional prognostic and therapeutic factor in gastric cancer, and deserves further investigation.

Adenocarcinoma↗

PubMed1994

Translational activity of mouse protamine 1 messenger ribonucleoprotein particles in the reticulocyte and wheat germ cell-free translation systems.

Protamine 1 mRNAs are inactivated by a block to the initiation of translation in early spermatids and are translationally active in late spermatids in mice. To determine whether translation of protamine 1 mRNAs is inhibited by a protein repressor, the translational activity of ribonucleoprotein particles and deproteinized RNAs were compared in the reticulocyte and wheat germ cell-free translation lysates. To isolate RNPs, cytoplasmic extracts of total testes were fractionated by large-pore gel filtration chromatography. Ribonucleoprotein particles in the excluded fractions stimulated synthesis of radiolabeled translation products for protamine 1 about twofold less effectively than deproteinized RNAs in the reticulocyte lysate, but were inactive in the wheat germ lysate. The ability of translationally repressed protamine 1 ribonucleoprotein particles to form initiation complexes with 80S ribosomes in the reticulocyte lysate was also measured. Protamine 1 ribonucleoprotein particles isolated by gel filtration and in unfractionated cytoplasmic extracts of early spermatids were nearly as active in forming initiation complexes as deproteinized mRNAs. The isolation of ribonucleoprotein particles in buffers of varying ionic strength, protease inhibitors, and several other variables had no major effect on the ability of protamine 1 ribonucleoprotein particles to form initiation complexes in the reticulocyte lysate. These results can be explained by artifacts in the isolation or assay of ribonucleoprotein particles or by postulating that protamine 1 mRNAs are inactivated by a mechanism that does not involve protein repressors, such as sequestration.

Animals↗

PubMed1994

Developmental expression of poly(A) binding protein mRNAs during spermatogenesis in the mouse.

The poly(A) binding protein (PABP), a conserved protein that binds to the 3' poly(A) tail on mRNAs in eukaryotic cells, has been implicated in the regulation of mRNA stability and translation. Two PABP cDNAs with different sequences were isolated from mouse testis cDNA libraries. The predicted amino acid sequence of one, PABP1, is nearly identical (98.9%) to human liver PABP, while 80% of the amino acids of the second, PABPt, are identical to mouse and human PABPs. Northern blots reveal that there is one major PABP mRNA species in liver, muscle, kidney, and brain, two in spleen, and at least four in testis. The levels of PABP mRNA in testis are 5-10-fold higher than in these somatic tissues, but surprisingly the vast majority of all PABP mRNA size variants sediment more slowly than single ribosomes, indicating strong translational repression. Reverse transcriptase-polymerase chain reaction assays demonstrate that PABPt mRNAs are abundant only in testis. Northern blots of RNAs purified from highly enriched spermatogenic cells show that the high levels, multiple sizes of PABP mRNAs, and the PABPt mRNA are present in meiotic and early haploid spermatogenic cells, and are sharply reduced in late haploid cells. Comparison of the binding of PABP1 and PABPt to poly(A) Sepharose in vitro revealed subtle differences, even though PABPt contains substitutions for highly conserved aromatic amino acids that are thought to be necessary for binding to poly(A). The existence of two PABP isoforms in mouse spermatogenic cells could influence cytoplasmic gene expression during spermatogenesis.

Amino Acid Sequence↗