In addition to alternative splicing, which occurs in one tissue or another for some 95 percent of human genes, alternative polyadenylation occurs for some 50 percent of human mRNAs. Alternative polyadenylation results from the use of two or more alternative polyadenylation signals in different cell types. In some cases, this appears to be due to different concentrations of cleavage/polyadenylation factors in different cell types coupled with alternative poly(A) signals that have higher or lower affinity for the CStF complex that binds the downstream G/U-rich portion of the cleavage/poly adenylation signal. In these cases, when the concentration of CStF is low, only the highest-affinity polyadenylation signals are used. But in alternative cell types where the CStF concentration is higher, an upstream low-affinity site is used preferentially because once the pre mRNA is cleaved, the downstream site cannot be used. In other cases, sequence-specific RNA-binding proteins may block or enhance binding of the cleavage/polyadenylation factors, as in the case of splicing repressors and activators.

When multiple mRNAs expressed from the same gene use alternative polyadenylation sites, additional miRNA binding sites may be located in the mRNA with the longer 3′ exon. As a consequence, mRNAs with the same protein coding sequence may be regulated differently in different cell types depending on the length of the 3′ UTR and the miRNAs expressed in those cells. Consequently, alternative polyadenylation can regulate the translation of mRNAs encoding the same protein as a consequence of miRNA control of translation and mRNA stability.

Alternative sites of polyadenylation can also be coupled to alternative splicing of the final exon in an mRNA. As a consequence, protein isoforms can be expressed that have different C-terminal amino acid sequences. This type of variation is observed in the expression of alternative immunoglobulin molecules during B-lymphocyte development. Initially, an immunoglobulin antibody is produced with a transmembrane domain, which anchors the antibody in the plasma membrane, and a cytoplasmic domain, which signals when the antigen-binding extracellular domain encounters antigen—the molecule bound by an antibody. When antigen is bound, processing of the pre mRNA is modified so that an alternative 3′ exon is included in the mRNA. The antibody molecules translated from this alternatively processed mRNA lack the transmembrane domain, and as a consequence, they are secreted into the extracellular space, where they can neutralize pathogens.

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اخبار العتبة العباسية المقدسة

قسم الشؤون الفكريّة يُهدي إصداراته العلمية إلى مكتبات محافظة كركوك

شعبة فاطمة بنت أسد تطلق مسابقتها الإلكترونية (منارة الجود في مهد الصبا) لكتابة القصة للأطفال

المجمع العلمي يقيم برنامجًا قرآنيًا تعليميًا في النجف الأشرف

قسم الشؤون الدينية يقيم مجلسًا عزائيًّا لاستذكار أهل البيت (عليهم السلام)

المزيد

الآخبار الصحية

ما هي أفضل العصائر لصحة القلب وتقوية المناعة والنوم العميق؟

الأطعمة الغنية بالبروتينات النباتية تقلل خطر الأمراض المزمنة

وجع الأوتار قد يخفي خطرا صحيا مرتبطا بالقلب

أزمة "السفينة الموبوءة"..الأرجنتين تحقق في مصدر تفشي "هانتا"

المزيد

الآخبار التكنلوجية

باحثون يحددون تأثير القهوة على الميكروبيوم والمزاج

روسيا.. ابتكار تقنية لمعالجة سبائك التيتانيوم لحماية الطائرات والسيارات

بكين وواشنطن تدرسان إطلاق محادثات رسمية حول الذكاء الاصطناعي

لأول مرة في الولايات المتحدة.. تشغيل مفاعل مصغر نووي يغذي الذكاء الاصطناعي بالطاقة

المزيد

مواضيع ذات صلة

Protein Synthesis Can Be Globally Regulated

Cytoplasmic Polyadenylation Promotes Translation of Some mRNAs

RNA Interference Induces Degradation of Precisely Complementary mRNAs

Micro-RNAs Repress Translation and Induce Degradation of Specific mRNAs

Degradation of mRNAs in the Cytoplasm Occurs by Several Mechanisms

RNA Processing Solves the Problem of Pervasive Transcription of the Genome in Metazoans

Nuclear Exoribonucleases Degrade RNA That Is Processed Out of Pre-mRNAs

Microchip Electrophoresis

Electrophoresis of RNA

Pulsed-Field Gel Electrophoresis

3′ Cleavage and Polyadenylation of Pre-mRNAs Are Tightly Coupled

Self-Splicing Group II Introns Provide Clues to the Evolution of snRNAs