Identification of functional microRNAs released through asymmetrical processing of HIV-1 TAR element.
The interaction between human immunodeficiency virus type 1 (HIV-1) and RNA silencing pathways is complex and multifaceted. Essential for efficient viral transcription and supporting Tat-mediated transactivation of viral gene expression, the trans-activation responsive (TAR) element is a structured RNA located at the 5' end of all transcripts derived from HIV-1. Here, we report that this element is a source of microRNAs (miRNAs) in cultured HIV-1-infected cell lines and in HIV-1-infected human CD4+ T lymphocytes. Using primer extension and ribonuclease (RNase) protection assays, we delineated both strands of the TAR miRNA duplex deriving from a model HIV-1 transcript, namely miR-TAR-5p and miR-TAR-3p. In vitro RNase assays indicate that the lack of a free 3' extremity at the base of TAR may contribute to its low processing reactivity in vivo. Both miR-TAR-5p and miR-TAR-3p down-regulated TAR miRNA sensor activity in a process that required an integral miRNA-guided RNA silencing machinery. miR-TAR-3p exerted superior gene downregulatory effects, probably due to its preferential release from HIV-1 TAR RNA by the RNase III Dicer. Our study suggests that the TAR element of HIV-1 transcripts releases functionally competent miRNAs upon asymmetrical processing by Dicer, thereby providing novel insights into viral miRNA biogenesis.
Ouellet
Dominique L
DL
Centre de Recherche en Rhumatologie et Immunologie, Quebec, QC, G1V 4G2, Canada.
Plante
Isabelle
I
Landry
Patricia
P
Barat
Corinne
C
Janelle
Marie-Eve
ME
Flamand
Louis
L
Tremblay
Michel J
MJ
Provost
Patrick
P
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D051379:Mice; D035683:MicroRNAs / Q000378:metabolism*; D008969:Molecular Sequence Data; D012323:RNA Processing, Post-Transcriptional; D012367:RNA, Viral / Q000737:chemistry / Q000378:metabolism; D043244:Ribonuclease III / Q000378:metabolism
D051860:Fragile X Messenger Ribonucleoprotein 1; D035683:MicroRNAs; D012367:RNA, Viral; D043244:Ribonuclease III