Smad proteins bind a conserved RNA sequence to promote microRNA maturation by Drosha.
The signal transducers of the transforming growth factor beta (TGFbeta)/bone morphogenetic protein (BMP), the Smads, promote the expression of a subset of miRNAs by facilitating the cleavage reaction by Drosha. The mechanism that limits Smad-mediated processing to a selective group of miRNAs remained hitherto unexplored. In this study, we expand the number of TGFbeta/BMP-regulated miRNAs (T/B-miRs) to 20. Of interest, a majority of T/B-miRs contain a consensus sequence (R-SBE) within the stem region of the primary transcripts of T/B-miRs (pri-T/B-miRs). Here, we demonstrate that Smads directly bind the R-SBE. Mutation of the R-SBE abrogates TGFbeta/BMP-induced recruitment of Smads, Drosha, and DGCR8 to pri-T/B-miRs and impairs their processing, whereas introduction of R-SBE to unregulated pri-miRNAs is sufficient to recruit Smads and to allow regulation by TGFbeta/BMP. Thus, Smads are multifunctional proteins that modulate gene expression transcriptionally through DNA binding and posttranscriptionally through pri-miRNA binding and regulation of miRNA processing.
Davis
Brandi N
BN
Department of Biochemistry, Tufts University School of Medicine, Boston, MA 02111, USA.
Hilyard
Aaron C
AC
Nguyen
Peter H
PH
Lagna
Giorgio
G
Hata
Akiko
A
D002478:Cells, Cultured; D006801:Humans; D053505:Matrix Metalloproteinases, Secreted / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects / Q000502:physiology*; D016601:RNA-Binding Proteins; D038621:Regulatory Sequences, Ribonucleic Acid / Q000502:physiology*; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism*; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology
C474043:DGCR8 protein, human; D035683:MicroRNAs; D011506:Proteins; D016601:RNA-Binding Proteins; D038621:Regulatory Sequences, Ribonucleic Acid; D051785:Smad Proteins; D016212:Transforming Growth Factor beta; C517918:DROSHA protein, human; D043244:Ribonuclease III; D053505:Matrix Metalloproteinases, Secreted