Interaction between the human nuclear cap-binding protein complex and hnRNP F

European Molecular Biology Laboratory, Heidelberg, Germany.
Molecular and Cellular Biology (Impact Factor: 4.78). 06/1997; 17(5):2587-97. DOI: 10.1128/MCB.17.5.2587
Source: PubMed


hnRNP F was identified in a screen for proteins that interact with human CBP80 and CBP20, the components of the nuclear cap-binding
complex (CBC). In vitro interaction studies showed that hnRNP F can bind to both CBP20 and CBP80 individually. hnRNP F and
CBC bind independently to RNA, but hnRNP F binds preferentially to CBC-RNA complexes rather than to naked RNA. The hnRNP H
protein, which is 78% identical to hnRNP F and also interacts with both CBP80 and CBP20 in vitro, does not discriminate between
naked RNA and CBC-RNA complexes, showing that this effect is specific. Depletion of hnRNP F from HeLa cell nuclear extract
decreases the efficiency of pre-mRNA splicing, a defect which can be partially compensated by addition of recombinant hnRNP
F. Thus, hnRNP F is required for efficient pre-mRNA splicing in vitro and may participate in the effect of CBC on pre-mRNA

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Available from: Elisa Izaurralde, Sep 09, 2014
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    • "Indeed, hnRNP F was reported to be engaged in alternative splicing of c-src (24), β-tropomyosin gene (25), thyroid hormone receptor gene (26), Bcl-x gene (27,28), and p53 gene (29) as well as in the 3′-end processing of pre-mRNA in B-cell differentiation (30). hnRNP F is also associated with TATA-binding protein, RNA polymerase II, and even with the nuclear cap-binding protein complex (31,32). The molecular mechanism of hnRNP F action on gene transcription, however, is not well-defined. "
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    ABSTRACT: We investigated the impact of heterogeneous nuclear ribonucleoprotein F (hnRNP F) overexpression on angiotensinogen (Agt) gene expression, hypertension, and renal proximal tubular cell (RPTC) injury in high-glucose milieu both in vivo and in vitro. Diabetic Akita transgenic (Tg) mice specifically overexpressing hnRNP F in their RPTCs were created, and the effects on systemic hypertension, Agt gene expression, renal hypertrophy, and interstitial fibrosis were studied. We also examined immortalized rat RPTCs stably transfected with control plasmid or plasmid containing hnRNP F cDNA in vitro. The results showed that hnRNP F overexpression attenuated systemic hypertension, suppressed Agt and transforming growth factor-β1 (TGF-β1) gene expression, and reduced urinary Agt and angiotensin II levels, renal hypertrophy, and glomerulotubular fibrosis in Akita hnRNP F-Tg mice. In vitro, hnRNP F overexpression prevented the high-glucose stimulation of Agt and TGF-β1 mRNA expression and cellular hypertrophy in RPTCs. These data suggest that hnRNP F plays a modulatory role and can ameliorate hypertension, renal hypertrophy, and interstitial fibrosis in diabetes. The underlying mechanism is mediated, at least in part, via the suppression of intrarenal Agt gene expression in vivo. hnRNP F may be a potential target in the treatment of hypertension and kidney injury in diabetes.
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    • "Several types of hnRNP proteins are well known regulators of AS and some of them have also been reported to play a role in constitutive splicing. The depletion of hnRNP F (Gamberi et al., 1997) or hnRNP Q (Mourelatos et al., 2001), for instance, resulted in diminished in vitro splicing activity. Furthermore, using mass spectrometry, hnRNP proteins were identified as components of purified ribosomes in mammals (Neubauer et al., 1998). "
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    ABSTRACT: Alternative precursor mRNA splicing is a widespread phenomenon in multicellular eukaryotes and represents a major means for functional expansion of the transcriptome. While several recent studies have revealed an important link between splicing regulation and fundamental biological processes in plants, many important aspects, such as the underlying splicing regulatory mechanisms, are so far not well understood. Splicing decisions are in general based on a splicing code that is determined by the dynamic interplay of splicing-controlling factors and cis-regulatory elements. Several members of the group of heterogeneous nuclear ribonucleoprotein (hnRNP) proteins are well known regulators of splicing in animals and the comparatively few reports on some of their plant homologs revealed similar functions. This also applies to polypyrimidine tract-binding proteins, a thoroughly investigated class of hnRNP proteins with splicing regulatory functions in both animals and plants. Further examples from plants are auto- and cross-regulatory splicing circuits of glycine-rich RNA binding proteins and splicing enhancement by oligouridylate binding proteins. Besides their role in defining splice site choice, hnRNP proteins are also involved in multiple other steps of nucleic acid metabolism, highlighting the functional versatility of this group of proteins in higher eukaryotes.
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    • "The molecular machinery regulating cotranscriptional RNA metabolism is still not well understood, particularly in plants. Work in yeast and humans has shown that the CBC, composed of the two conserved subunits CBC80 and CBC20, associates with the CTD of RNA polymerase II and is required for many aspects of RNA splicing, RNA stability, and export and has been proposed to affect transcriptional elongation via a checkpoint mechanism (Gamberi et al., 1997; Shatkin and Manley, 2000). Our analysis reveals that FRI is a direct interactor of the CBC, with suppression of FRI activity by both cbp20 and cbp80 providing in vivo endorsement of the importance of the CBC for FRI function. "
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