Protein lin-28 homolog B (Lin-28B)
1_MAEGG 6_ ASKGG 11_ GEEPG 16_ KLPEP 21_ AEEES 26_ QVLRG 31_ TGHCK 36_ WFNVR 41_ MGFGF 46_ ISMIN 51_ REGSP 56_ LDIPV 61_ DVFVH 66_ QSKLF 71_ MEGFR 76_ SLKEG 81_ EPVEF 86_ TFKKS 91_ SKGLE 96_ SIRVT 101_ GPGGS 106_ PCLGS 111_ ERRPK 116_ GKTLQ 121_ KRKPK 126_ GDRCY 131_ NCGGL 136_ DHHAK 141_ ECSLP 146_ PQPKK 151_ CHYCQ 156_ SIMHM 161_ VANCP 166_ HKNVA 171_ QPPAS 176_ SQGRQ 181_ EAESQ 186_ PCTST 191_ LPREV 196_ GGGHG 201_ CTSPP 206_ FPQEA 211_ RAEIS 216_ ERSGR 221_ SPQEA 226_ SSTKS 231_ SIAPE 236_ EQSKK 241_GPSVQ
1: Suppressor of microRNA (miRNA) biogenesis, including that of let-7 and possibly of miR107, miR-143 and miR-200c. Binds primary let-7 transcripts (pri-let-7), including pri-let-7g and pri-let-7a-1, and sequester them in the nucleolus, away from the microprocessor complex, hence preventing their processing into mature miRNA (PubMed:22118463). Does not act on pri-miR21 (PubMed:22118463). The repression of let-7 expression is required for normal development and contributes to maintain the pluripotent state of embryonic stem cells by preventing let-7-mediated differentiation. When overexpressed, recruits ZCCHC11/TUT4 uridylyltransferase to pre-let-7 transcripts, leading to their terminal uridylation and degradation (PubMed:19703396). This activity might not be relevant in vivo, as LIN28B-mediated inhibition of let-7 miRNA maturation appears to be ZCCHC11-independent (PubMed:22118463). Interaction with target pre-miRNAs occurs via an 5'-GGAG-3' motif in the pre-miRNA terminal loop. Mediates MYC-induced let-7 repression (By similarity). When overexpressed, isoform 1 stimulates growth of the breast adenocarcinoma cell line MCF-7. Isoform 2 has no effect on cell growth