Importance of the NCp7-like domain in the recognition of pre-let-7g by the pluripotency factor Lin28.
The pluripotency factor Lin28 is a highly conserved protein comprising a unique combination of RNA-binding motifs, an N-terminal cold-shock domain and a C-terminal region containing two retroviral-type CCHC zinc-binding domains. An important function of Lin28 is to inhibit the biogenesis of the let-7 family of microRNAs through a direct interaction with let-7 precursors. Here, we systematically characterize the determinants of the interaction between Lin28 and pre-let-7 g by investigating the effect of protein and RNA mutations on in vitro binding. We determine that Lin28 binds with high affinity to the extended loop of pre-let-7 g and that its C-terminal domain contributes predominantly to the affinity of this interaction. We uncover remarkable similarities between this C-terminal domain and the NCp7 protein of HIV-1, not only in terms of primary structure but also in their modes of RNA binding. This NCp7-like domain of Lin28 recognizes a G-rich bulge within pre-let-7 g, which is adjacent to one of the Dicer cleavage sites. We hypothesize that the NCp7-like domain initiates RNA binding and partially unfolds the RNA. This partial unfolding would then enable multiple copies of Lin28 to bind the extended loop of pre-let-7 g and protect the RNA from cleavage by the pre-microRNA processing enzyme Dicer.
Département de Biochimie, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, QC, Canada H3C 3J7.
Alexandre
A
Desjardins
Ao
A
Yang
Jonathan
J
Bouvette
James G
JG
Omichinski
Pascale
P
Legault
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D051379:Mice; D035683:MicroRNAs / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012322:RNA Precursors / Q000737:chemistry* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000737:chemistry
C488352:Lin-28 protein, mouse; D035683:MicroRNAs; C071884:NCP7 protein, Human immunodeficiency virus 1; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus; C542687:mirnlet7 microRNA, mouse