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Specific combinations of SR proteins associate with single pre-messenger RNAs in vivo and contribute different functions.

Björk P, Jin S, Zhao J, Singh OP, Persson JO, Hellman U, Wieslander L - J. Cell Biol. (2009)

Bottom Line: However, hrp45/SRp55 is distributed differently in the pre-mRNPs along the gene compared with ASF/SF2, SC35, and 9G8, suggesting functional differences.All four SR proteins are associated with the BR mRNPs during export to the cytoplasm.ASF/SF2 is associated with polyribosomes, whereas SC35, 9G8, and hrp45/SRp55 cosediment with monoribosomes.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Functional Genomics, Stockholm University, SE-106 91 Stockholm, Sweden.

ABSTRACT
Serine/arginine-rich (SR) proteins are required for messenger RNA (mRNA) processing, export, surveillance, and translation. We show that in Chironomus tentans, nascent transcripts associate with multiple types of SR proteins in specific combinations. Alternative splicing factor (ASF)/SF2, SC35, 9G8, and hrp45/SRp55 are all present in Balbiani ring (BR) pre-messenger ribonucleoproteins (mRNPs) preferentially when introns appear in the pre-mRNA and when cotranscriptional splicing takes place. However, hrp45/SRp55 is distributed differently in the pre-mRNPs along the gene compared with ASF/SF2, SC35, and 9G8, suggesting functional differences. All four SR proteins are associated with the BR mRNPs during export to the cytoplasm. Interference with SC35 indicates that SC35 is important for the coordination of splicing, transcription, and 3' end processing and also for nucleocytoplasmic export. ASF/SF2 is associated with polyribosomes, whereas SC35, 9G8, and hrp45/SRp55 cosediment with monoribosomes. Thus, individual endogenous pre-mRNPs/mRNPs bind multiple types of SR proteins during transcription, and these SR proteins accompany the mRNA and play different roles during the gene expression pathway in vivo.

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Different types of SR proteins are associated with BR gene loci. (A–F) Chromosome IV was immunostained with combinations of anti-9G8 and anti-hrp45/SRp55 antibodies (A–C) or anti-9G8 and anti-SC35 antibodies (D–F). Arrows indicate the active BR1, BR2, and BR3 gene loci. The arrowheads show a fourth gene locus containing 9G8 and SC35 but little hrp45/SRp55. Bar, 10 µm.
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fig2: Different types of SR proteins are associated with BR gene loci. (A–F) Chromosome IV was immunostained with combinations of anti-9G8 and anti-hrp45/SRp55 antibodies (A–C) or anti-9G8 and anti-SC35 antibodies (D–F). Arrows indicate the active BR1, BR2, and BR3 gene loci. The arrowheads show a fourth gene locus containing 9G8 and SC35 but little hrp45/SRp55. Bar, 10 µm.

Mentions: Only a few genes have been characterized in C. tentans, and the identification of individual genes is only possible in specific cases in the chromosome preparations. On chromosome IV, the three BR gene loci, BR1, BR2, and BR3 (Wieslander, 1994), contained substantial amounts of all four SR proteins (Fig. 2, A–F; and Fig. S4 A). Quantification of double-stained chromosomes revealed that the BR1 and BR2 genes were very similar and that the BR3 gene contained a relatively higher proportion of SC35. Another gene locus contained 9G8, SC35, and ASF/SF2 but very little hrp45/SRp55 (Fig. 2, A, B, D, and E, arrowheads; and Fig. S4 A, arrowheads).


Specific combinations of SR proteins associate with single pre-messenger RNAs in vivo and contribute different functions.

Björk P, Jin S, Zhao J, Singh OP, Persson JO, Hellman U, Wieslander L - J. Cell Biol. (2009)

Different types of SR proteins are associated with BR gene loci. (A–F) Chromosome IV was immunostained with combinations of anti-9G8 and anti-hrp45/SRp55 antibodies (A–C) or anti-9G8 and anti-SC35 antibodies (D–F). Arrows indicate the active BR1, BR2, and BR3 gene loci. The arrowheads show a fourth gene locus containing 9G8 and SC35 but little hrp45/SRp55. Bar, 10 µm.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2654125&req=5

fig2: Different types of SR proteins are associated with BR gene loci. (A–F) Chromosome IV was immunostained with combinations of anti-9G8 and anti-hrp45/SRp55 antibodies (A–C) or anti-9G8 and anti-SC35 antibodies (D–F). Arrows indicate the active BR1, BR2, and BR3 gene loci. The arrowheads show a fourth gene locus containing 9G8 and SC35 but little hrp45/SRp55. Bar, 10 µm.
Mentions: Only a few genes have been characterized in C. tentans, and the identification of individual genes is only possible in specific cases in the chromosome preparations. On chromosome IV, the three BR gene loci, BR1, BR2, and BR3 (Wieslander, 1994), contained substantial amounts of all four SR proteins (Fig. 2, A–F; and Fig. S4 A). Quantification of double-stained chromosomes revealed that the BR1 and BR2 genes were very similar and that the BR3 gene contained a relatively higher proportion of SC35. Another gene locus contained 9G8, SC35, and ASF/SF2 but very little hrp45/SRp55 (Fig. 2, A, B, D, and E, arrowheads; and Fig. S4 A, arrowheads).

Bottom Line: However, hrp45/SRp55 is distributed differently in the pre-mRNPs along the gene compared with ASF/SF2, SC35, and 9G8, suggesting functional differences.All four SR proteins are associated with the BR mRNPs during export to the cytoplasm.ASF/SF2 is associated with polyribosomes, whereas SC35, 9G8, and hrp45/SRp55 cosediment with monoribosomes.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology and Functional Genomics, Stockholm University, SE-106 91 Stockholm, Sweden.

ABSTRACT
Serine/arginine-rich (SR) proteins are required for messenger RNA (mRNA) processing, export, surveillance, and translation. We show that in Chironomus tentans, nascent transcripts associate with multiple types of SR proteins in specific combinations. Alternative splicing factor (ASF)/SF2, SC35, 9G8, and hrp45/SRp55 are all present in Balbiani ring (BR) pre-messenger ribonucleoproteins (mRNPs) preferentially when introns appear in the pre-mRNA and when cotranscriptional splicing takes place. However, hrp45/SRp55 is distributed differently in the pre-mRNPs along the gene compared with ASF/SF2, SC35, and 9G8, suggesting functional differences. All four SR proteins are associated with the BR mRNPs during export to the cytoplasm. Interference with SC35 indicates that SC35 is important for the coordination of splicing, transcription, and 3' end processing and also for nucleocytoplasmic export. ASF/SF2 is associated with polyribosomes, whereas SC35, 9G8, and hrp45/SRp55 cosediment with monoribosomes. Thus, individual endogenous pre-mRNPs/mRNPs bind multiple types of SR proteins during transcription, and these SR proteins accompany the mRNA and play different roles during the gene expression pathway in vivo.

Show MeSH