Format

Send to

Choose Destination
Cell Cycle. 2009 Feb 1;8(3):345-56. Epub 2009 Feb 21.

Subnuclear compartmentalization of transiently expressed polyadenylated pri-microRNAs: processing at transcription sites or accumulation in SC35 foci.

Author information

1
Department of Pharmacology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536, USA.

Abstract

MicroRNAs (miRNAs) are small, noncoding RNAs that post-transcriptionally regulate expression of their target messenger RNAs. We recently demonstrated that primary miRNA transcripts (pri-miRNAs) retained at transcription sites are processed with enhanced efficiency, suggesting that pri-miRNA processing is coupled to transcription in mammalian cells. We also observed that transiently expressed pri-miRNAs accumulate in nuclear foci with splicing factor SC35 and Microprocessor components, Drosha and DGCR8. Here, we show that pri-miRNAs containing a self-cleaving hepatitis delta ribozyme accumulate in the nucleoplasm after release from their transcription sites, but are not efficiently processed. Pri-miRNAs with ribozyme-generated 3' ends do not localize to SC35-containing foci, whereas cleaved and polyadenylated pri-miRNA transcripts with or without the pre-miRNA hairpin do. Pri-miRNA/SC35 foci contain a number of proteins normally associated with SC35 domains, including ASF/SF2, PABII, and the prolyl isomerase, Pin1. In contrast, RNA polymerase II and PM/Scl-100 do not strongly colocalize with pri-miRNAs in SC35-containing foci. These data argue that pri-miRNA/SC35-containing foci are not major sites of pri-miRNA processing and that pri-miRNA processing is coupled to transcription. We discuss the implications of our findings relative to recent insights into miRNA biogenesis, mRNA metabolism, and the nuclear organization of gene expression.

PMID:
19177009
PMCID:
PMC3004524
DOI:
10.4161/cc.8.3.7494
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Taylor & Francis Icon for PubMed Central
Loading ...
Support Center