The hnRNP F protein: unique primary structure, nucleic acid-binding properties, and subcellular localization

Abstract

More than 20 different heterogeneous nuclear ribonucleoproteins (hnRNPs) are associated with premRNAs in the nucleus of mammalian cells and these proteins appear to influence pre-mRNA processing and other aspects of mRNA metabolism and transport. The arrangement of hnRNP proteins on pre-mRNAs is likely to be unique for each RNA and may be determined by the different RNA-binding preferences of each of these proteins. hnRNP F (Mr = 53 kD, pi = 6.1) and hnRNP H (Mr = 56 kD, pl = 6.7-7.1) are abundant components of immunopurified hnRNP complexes and they have distinct nucleic acid binding properties. Unlike other hnRNP proteins which display a varying range of affinities for different ribonucleotidehomopolymers and ssDNA, hnRNP F and hnRNP H bind only to poly(rG) in vitro. hnRNP F and hnRNP H were purified from HeLa cells by poly(rG) affinity chromatography and oligonucleotides derived from peptide sequences were used to isolate a cDNA encoding hnRNP F. The predicted amino acid sequence of hnRNP F revealed a novel protein with three repeated domains related to the RNP consensus sequence RNA-binding domain. Monoclonal antibodies produced against bacterially expressed hnRNP F were specific for both hnRNP F and hnRNP H and recognized related proteins in divergent organisms, including in the yeast Saccharomyces cerevisiae. hnRNP F and hnRNP H are thus highly related immunologically and they share identical peptides. Interestingly, immunofluorescence microscopy revealed that hnRNP F and hnRNP H are concentrated in discrete regions of the nucleoplasm, in contrast to the general nucleoplasmic distribution of previously characterized hnRNP proteins. The unique RNA-binding properties, amino acid sequence and distinct intranuclear localization of hnRNP F and hnRNP H make them novel hnRNP proteins that are likely to be important for the processing of RNAs containing guanosine-rich sequences.

Identification of Human Common Nuclear‐Matrix Proteins as Heterogeneous Nuclear Ribonucleoproteins H and H′ by Sequencing and Mass Spectrometry

“…Searches for proteins with identity to the found sequences were performed as described in Materials and Methods, using available public databases. Proteins showing the highest identities are listed in Table 1 [23,[27][28][29]. The sequence (HTGPNSPDTA) was 100% identical to sequences in human hnRNP H, hnRNP H' and ORF-FTP-3.…”

High-throughput analyses of hnRNP H1 dissects its multi-functional aspect

“…This protein tends to form a heterodimer with hnRNP F and shows preference for G-rich tracts of RNA. 2,[6][7][8] It has also been shown that hnRNP H1 interacts with the DGCR8 complex and facilitates microRNA processing in HeLa cells. 9 The impact of hnRNP H1 binding on alternative splicing has been associated with several diseases, such as cystic fibrosis, 10 congenital myasthemic syndrome, 11 and amyotrophic lateral sclerosis (ALS).…”

Structural basis of G-tract recognition and encaging by hnRNP F quasi-RRMs

“…G-tracts are also abundant downstream of mammalian polyadenylation signals 7 and in 5' and 3' untranslated regions (UTR) 8 . Some of the trans-acting factors that bind to these G-tracts belong to the heterogeneous nuclear ribonucleoprotein (hnRNP) F/H family of proteins that consists of five members (hnRNP F, hnRNP H, hnRNP H', hnRNP 2H9, and GRich Sequence Factor (GRSF) 1) 9,10 . GRSF-1 is mainly involved in translation regulation 11,12 and Internal Ribosome Entry Site (IRES) mediated translation 13 , while hnRNP H, H' and F are mostly involved in the regulation of alternative splicing [14][15][16][17][18][19][20][21][22][23] and polyadenylation [24][25][26] .…”

“…These proteins are very similar in sequence (hnRNP F and H share 78% sequence identity) 10,41 . The RNA binding domains of hnRNP F/H proteins were denoted qRRMs because of their similarity to the classical RRM motif.…”