Pseudouridine synthases modify human pre-mRNA co-transcriptionally and affect pre-mRNA processing

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Hybridization of mRNA and pre-mRNA with the sequences forming double-stranded structures in pre-mRNA

About 25% of the double-stranded sequences isolated from pre-mRNA are able to hybridize, after melting, with either mRNA or non-melted pre-mRNA. The retention of one branch of pre-mRNA hairpin in mRNA was suggested. It was also found that in addition to the hairpin-like structures comprising about 3% of the total sequences another 15% of the pre-mRNA sequences can form double-stranded structures upon annealing over a broad interval of Cot values.     

Human pre-mRNA splicing signals.

A sample of 764 pairs of human pre-mRNA exon-intron and intron-exon boundaries, extracted from the European Molecular Biology Laboratory data bank, is analyzed to provide a species-optimized characterization of donor and acceptor sites, evaluate the information content of the two signals (found to be about 8 and 9 bits respectively) and check the independent-base approximation (which holds well) and the "GT-AG" rule (to which, a few well-documented exceptions are found). No correlation is detected between the strength ("discrimination energy") of an actual donor-site signal and that of its corresponding acceptor-site counterpart, nor between that of either signal, or the cumulative strength of both, and the length of the intervening intron. The discrimination-energy distributions of the two signals are determined. Because of the large sample size and its single-species origin, the two distributions can be presumed to be representative of their underlying genomic counterparts. The size distribution of the introns shows a lower cut-off of 70 nucleotides (in essential agreement with published experimental results), and apparently no periodicities. A smaller sample of mammalian branch sites, taken from the literature, is similarly analyzed to attempt a characterization of this rather elusive signal, and provides some indication that at least part of the "long pyrimidine stretch", usually considered an integral constituent of the 3' splice signal, may be just as strongly associated with the branch site, in agreement with recent experimental observations. The usefulness of these characterizations for splice-junction searches is assessed on a test sequence.     

Temperature-dependent splicing of beta-globin pre-mRNA

A T→G mutation at nucleotide 705 of human β-globin intron 2 creates an aberrant 5′ splice site and activates a cryptic 3′ splice site upstream. In consequence, the pre-mRNA is spliced via aberrant splice sites, despite the presence of the still functional correct sites. Surprisingly, when IVS2-705 HeLa or K562 cells were cultured at temperatures below 30°C, aberrant splicing was inhibited and correct splicing was restored. Similar temperature effects were seen for another β-globin pre-mRNA, IVS2-745, and in a construct in which a β-globin intron was inserted into a coding sequence of EGFP. Temperature-induced alternative splicing was affected by the nature of the internal aberrant splice sites flanking the correct sites and by exonic sequences. The results indicate that in the context of thalassemic splicing mutations and possibly in other alternatively spliced pre-mRNAs, temperature is one of the parameters that affect splice site selection.     

Regulation of mammalian pre-mRNA splicing

In eukaryotes, most protein-coding genes contain introns which are removed by precursor messenger RNA (pre-mRNA) splicing. Alternative splicing is a process by which multiple messenger RNAs (mRNAs) are generated from a single pre-mRNA, resulting in functionally distinct proteins. Recent genome-wide analyses of alternative splicing indicated that in higher eukaryotes alternative splicing is an important mechanism that generates proteomic complexity and regulates gene expression. Mis-regulation of splicing causes a wide range of human diseases. This review describes the current understanding of pre-mRNA splicing and the mechanisms that regulate mammalian pre-mRNA splicing. It also discusses emerging directions in the field of alternative splicing. Supported by the Program of “one Hundred Talented people” of the Chinese Academy of Sciences.     

Epigenetics in alternative pre-mRNA splicing

Alternative splicing plays critical roles in differentiation, development, and disease and is a major source for protein diversity in higher eukaryotes. Analysis of alternative splicing regulation has traditionally focused on RNA sequence elements and their associated splicing factors, but recent provocative studies point to a key function of chromatin structure and histone modifications in alternative splicing regulation. These insights suggest that epigenetic regulation determines not only what parts of the genome are expressed but also how they are spliced.     

Small molecule control of pre-mRNA splicing

SR proteins regulate alternative splicing by binding to exonic sequences where, via an arginine/serine-rich splicing activation domain, they enhance the binding of the spliceosome to the adjacent splice sites. Here, a system is described in which a nontoxic derivative of the small molecule rapamycin is used to control pre-mRNA splicing in vitro. This involves the rapamycin-dependent recruitment of a splicing activation domain located on one protein to a second protein bound to the pre-mRNA. These results provide a new approach to explore for regulating gene expression in vivo with small molecules by controlling pre-mRNA splicing.     

RNA helicase dynamics in pre-mRNA splicing

The DExH-box NTPase/helicase Prp22p plays two important roles in pre-mRNA splicing. It promotes the second transesterification reaction and then catalyzes the ATP-dependent release of mature mRNA from the spliceosome. Evidence that helicase activity is important emerged from the analysis of Prp22p motif III (SAT) mutations that uncouple the NTPase and helicase activities. We find that S635A and T637A hydrolyse ATP, but are defective in unwinding duplex RNA and releasing mRNA from the spliceosome. The S635A mutation is lethal in vivo at 相似文献   

mRNA前体的剪接因子

真核生物通过mRNA前体的剪接,包括选择性剪接机制,调控着自身的生长与发育,了解其基本过程和有关参与因子,对进一步探索真核生物基因的表达调控和分子进化都具有极其重要的意义.该文简要综述了mRNA前体剪接的基本过程及有关剪接因子的最新研究进展,介绍了SR蛋白（Ser-Arg rich protein）家族因子、某些新发现的参与形成核不均一核糖核蛋白（heterogeneous nuclear ribonucleoprotein,hnRNP）的因子及部分：RNA解旋酶等在mRNA前体剪接过程中的功能和作用.     

Structure of nuclear pre-mRNA. IX. Hybridization of double-stranded portions of pre-mRNA with excess mRNA

The hybridization of double-stranded regions of pre-mRNA from mouse Ehrlich ascites carcinoma cells, rabbit bone marrow cells and primary culture of rabbit kidney cells with an excess of total poly(A)+-mRNA of mouse or rabbit globin mRNA respectively was studied. The hybrids were detected as RNAase-stable acid precipitable material or by adsorbtion of the hybrid complexes of poly(U)-sepharose. The sizes of the hybrid complementary sequences and their thermal stability were estimated.