A Pre-mRNA-Binding Protein Accompanies the RNA from the Gene through the Nuclear Pores and into Polysomes

Visa, Neus; Alzhanova-Ericsson, Alla T.; Sun, Xin; Киселева, Елена; Björkroth, Birgitta; Wurtz, Tilmann; Daneholt, Bertil

doi:10.1016/s0092-8674(00)80980-0

Cited by 212 publications

(170 citation statements)

References 59 publications

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“…Moreover, hnRNP A1 depletion led to decreased Gag synthesis without any concomitant change in splicing or steady-state vRNA levels (23). Consistently, a previous study showed that an hnRNP A1 homolog remains associated with RNA during transit through the nuclear pores and during the loading onto polysomes (53). Cumulatively, this suggests a role for hnRNP A1 in translational regulation.…”

Section: Increased Expression and Cytoplasmic Accumulation Of Hnrnp Asupporting

confidence: 68%

Human Immunodeficiency Virus Type 1 (HIV-1) Induces the Cytoplasmic Retention of Heterogeneous Nuclear Ribonucleoprotein A1 by Disrupting Nuclear Import

Monette

Ajamian

López-Lastra

et al. 2009

Journal of Biological Chemistry

136

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Human immunodeficiency virus type 1 (HIV-1) co-opts host proteins and cellular machineries to its advantage at every step of the replication cycle. Here we show that HIV-1 enhances heterogeneous nuclear ribonucleoprotein (hnRNP) A1 expression and promotes the relocalization of hnRNP A1 to the cytoplasm. The latter was dependent on the nuclear export of the unspliced viral genomic RNA (vRNA) and to alterations in the abundance and localization of the FG-repeat nuclear pore glycoprotein p62. hnRNP A1 and vRNA remain colocalized in the cytoplasm supporting a post-nuclear function during the late stages of HIV-1 replication. Consistently, we show that hnRNP A1 acts as an internal ribosomal entry site trans-acting factor up-regulating internal ribosome entry site-mediated translation initiation of the HIV-1 vRNA. The up-regulation and cytoplasmic retention of hnRNP A1 by HIV-1 would ensure abundant expression of viral structural proteins in cells infected with HIV-1.During the late stages of the HIV-1 3 replication cycle, the full-length HIV-1 viral RNA (vRNA) must be exported from the nucleus and both translated and packaged into new viral particles (1). The orchestration of these events is directed by a diversity of viral and host proteins that interact with each other and with the vRNA to form HIV-1 ribonucleoprotein (RNP) complexes that originate in the nucleus and persist in the cytoplasm (2). Investigations into the composition and functions of the HIV-1 RNP will reveal new information about innate immunity as well as identify new potential therapeutic targets (3-6).The heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is a predominantly nuclear protein engaged in a number of cellular and viral RNPs for RNA-processing activities, including splicing regulation, nuclear export, microRNA processing, mRNA stability, telomere maintenance, and IRES-mediated translation initiation (7-12). What enables hnRNP A1 to have such broad functions in RNA metabolism is its ability to bind both nuclear and cytoplasmic RNAs (10). In addition to its well characterized role in nuclear RNA processing, hnRNP A1 binds to purine-rich sequences of mRNAs for mRNA turnover and translation (13,14). Close examination of the HIV-1 vRNA reveals many AG-and AU-rich sequences closely resembling hnRNP A1 binding motifs (15). In fact, hnRNP A1 binds to a number of sequences on the HIV-1 vRNA such as the cis-acting repressive sequences, instability elements, and exonic splicing silencer elements, and indeed, hnRNP A1 is implicated in the fate of HIV-1 RNA, including splicing regulation, nucleocytoplasmic export, and cytoplasmic stability (16 -21).Our previous work demonstrated that hnRNP A1 efficiently immunoprecipitated with the HIV-1 vRNA (22) and that siRNA-mediated knockdown of hnRNP A1 caused a dramatic decrease in HIV-1 structural protein, pr55Gag (herein termed Gag) expression and virus production with little effect on steady-state levels of the three HIV-1 RNA species (i.e. 9-, 4-, and 2-kb RNAs) (23). In this work, we show that HIV-1 ...

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Section: Increased Expression and Cytoplasmic Accumulation Of Hnrnp Asupporting

confidence: 68%

Human Immunodeficiency Virus Type 1 (HIV-1) Induces the Cytoplasmic Retention of Heterogeneous Nuclear Ribonucleoprotein A1 by Disrupting Nuclear Import

Monette

Ajamian

López-Lastra

et al. 2009

Journal of Biological Chemistry

136

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“…Among the proteins bound to this RNP particle, three distinct classes have been described, represented by (1) a protein related to human hnRNP A1, which exits the nucleus in association with the RNP particle and is found in the cytoplasm bound to polysomes (Visa et al 1996a); (2) CBP20, a cap-binding protein that travels across the nuclear membrane in association with the RNP particle but is released from the RNA immediately after crossing the nuclear membrane (Visa et al 1996b);and (3) an SR protein that is visualized in the nucleus as an RNP but never leaves the nucleus (Alzhanova-Ericsson et al 1996).…”

mentioning

confidence: 99%

A specific subset of SR proteins shuttles continuously between the nucleus and the cytoplasm

Cáceres¹,

Screaton²,

Krainer³

1998

Genes Dev.

434

351

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The SR proteins constitute a large family of nuclear phosphoproteins required for constitutive pre-mRNA splicing. These factors also have global, concentration-dependent effects on alternative splicing regulation and this activity is antagonized by members of the hnRNP A/B family of proteins. We show here that whereas some human SR proteins are confined to the nucleus, three of them-SF2/ASF, SRp20, and 9G8-shuttle rapidly and continuously between the nucleus and the cytoplasm. By swapping the corresponding domains between shuttling and nonshuttling SR proteins, we show that the carboxy-terminal arginine/serine-rich (RS) domain is required for shuttling. This domain, however, is not sufficient to promote shuttling of an unrelated protein reporter, suggesting that stable RNA binding mediated by the RNA-recognition motifs may be required for shuttling. Consistent with such a requirement, a double point-mutation in RRM1 of SF2/ASF that impairs RNA binding prevents the protein from shuttling. In addition, we show that phosphorylation of the RS domain affects the shuttling properties of SR proteins. These findings show that different SR proteins have unique intracellular transport properties and suggest that the family members that shuttle may have roles not only in nuclear pre-mRNA splicing but also in mRNA transport, cytoplasmic events, and/or processes that involve communication between the nucleus and the cytoplasm. The SR proteins are closely related, highly conserved RNA-binding proteins that have dual roles in pre-mRNA splicing. They are essential for constitutive splicing and also regulate splicing in a concentration-dependent manner by influencing the selection of alternative splice sites (Ge and Manley 1990; Krainer et al. 1990a,b;Zahler et al. 1993; for review, see Fu 1995; Manley and Tacke 1996; Cá ceres and Krainer 1997). The activity of SR proteins in regulated splicing is antagonized by members of the hnRNP A/B family of proteins (Mayeda and Krainer 1992;Mayeda et al. 1994) and alterations in the ratio of these antagonistic factors cause drastic changes in splice-site selection both in vitro and in vivo (Mayeda and Krainer 1992;Cá ceres et al. 1994;Yang et al. 1994). The relative abundance of each SR protein and the molar ratio of each SR protein to hnRNP A1 or to other antagonists may therefore determine the patterns of alternative splicing of many genes expressed in specific cell types. Tissue-specific variations in the total and relative amounts of SR proteins or mRNAs have been described (for review, see Cá ceres and Krainer 1997) and in addition, the molar ratio of SF2/ASF to hnRNPA1 varies over a wide range in different rat tissues (A. Hanamura, J.F. Cá ceres, A. Mayeda, and A.R. Krainer, in prep.).The SR proteins are nuclear phosphoproteins that are concentrated, together with most other splicing factors, in nuclear subregions termed speckles. The speckle domain seen by immunofluorescence corresponds to interchromatin granule clusters and perichromatin fibrils at the electron microscope level (f...

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“…1 Although hnRNPs were among the first eukaryotic RNA-binding proteins isolated, their role in vivo is complex and not fully delineated. hnRNP A1 is tightly associated with DNA polymerase II transcripts, and recent work has suggested that they may play an important role in the retention of introncontaining pre-mRNA within the nucleus (1) as well as already established roles in alternative splicing (2)(3)(4)(5)(6)(7)(8)(9)(10) and RNA transport (11)(12)(13)(14). In addition, hnRNP A1 has been demonstrated to bind purine-rich DNAs such as the human telomeric repeat (hTR) d(TTAGGG) n (15)(16)(17)(18) and mouse minisatellite (MN) repeat d(GGCAG) n (19).…”

mentioning

confidence: 99%

Structure-based Incorporation of 6-Methyl-8-(2-deoxy-β-ribofuranosyl)isoxanthopteridine into the Human Telomeric Repeat DNA as a Probe for UP1 Binding and Destabilization of G-tetrad Structures

Myers

Moore

Shamoo

2003

Journal of Biological Chemistry

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Heterogeneous ribonucleoprotein A1 (hnRNP A1) is an abundant nuclear protein that participates in RNA processing, alternative splicing, and chromosome maintenance. hnRNP A1 can be proteolyzed to unwinding protein (UP1), a 22.1-kDa protein that retains a high affinity for purine-rich single-stranded nucleic acids, including the human telomeric repeat (hTR) d(T-TAGGG) n . Using the structure of UP1 bound to hTR as a guide, we have incorporated the fluorescent guanine analog 6-MI at one of two positions within the DNA to facilitate binding studies. One is where 6-MI remains stacked with an adjacent purine, and another is where it becomes fully unstacked upon UP1 binding. The structures of both modified oligonucleotides complexed to UP1 were determined by x-ray crystallography to validate the efficacy of our design, and 6-MI has proven to be an excellent reporter molecule for single-stranded nucleic acid interactions in positions where there is a change in stacking environment upon complex formation. We have shown that UP1 affinity for d(TTAGGG) 2 is ϳ5 nM at 100 mM NaCl, pH 6.0, and our binding studies with d(TTAGG(6-MI)TTAGGG) show that binding is only modestly sensitive to salt and pH. UP1 also has a potent G-tetrad destabilizing activity that reduces the T m of the hTR sequence d(TAGGGT) 4 from 67.0°C to 36.1°C at physiological conditions (150 mM KCl, pH 7.0). Consistent with the structures determined by x-ray crystallography, UP1 is able to bind the hTR sequence in solution as a dimer and supports a model for hnRNP A1 binding to nucleic acids in arrays that may make a contiguous set of anti-parallel single-stranded nucleic acid binding clefts. These data suggest that seemingly disparate roles for hnRNP A1 in alternative splice site selection, RNA processing, RNA transport, and chromosome maintenance reflect its ability to bind a purine-rich consensus sequence (nYAGGn) and destabilize potentially deleterious G-tetrad structures.

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A Pre-mRNA-Binding Protein Accompanies the RNA from the Gene through the Nuclear Pores and into Polysomes

Cited by 212 publications

References 59 publications

Human Immunodeficiency Virus Type 1 (HIV-1) Induces the Cytoplasmic Retention of Heterogeneous Nuclear Ribonucleoprotein A1 by Disrupting Nuclear Import

Human Immunodeficiency Virus Type 1 (HIV-1) Induces the Cytoplasmic Retention of Heterogeneous Nuclear Ribonucleoprotein A1 by Disrupting Nuclear Import

A specific subset of SR proteins shuttles continuously between the nucleus and the cytoplasm

Structure-based Incorporation of 6-Methyl-8-(2-deoxy-β-ribofuranosyl)isoxanthopteridine into the Human Telomeric Repeat DNA as a Probe for UP1 Binding and Destabilization of G-tetrad Structures

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