Structural highlights
Disease
[LN28B_HUMAN] Neuroblastoma.
Function
[LN28B_HUMAN] Acts as a suppressor of microRNA (miRNA) biogenesis by specifically binding the precursor let-7 (pre-let-7), a miRNA precursor. Acts by binding pre-let-7 and recruiting ZCCHC11/TUT4 uridylyltransferase, leading to the terminal uridylation of pre-let-7. Uridylated pre-let-7 miRNAs fail to be processed by Dicer and undergo degradation. Specifically recognizes the 5'-GGAG-3' motif in the terminal loop of pre-let-7. Also recognizes and binds non pre-let-7 pre-miRNAs that contain the 5'-GGAG-3' motif in the terminal loop, leading to their terminal uridylation and subsequent degradation. Mediates MYC-mediated let-7 repression. Isoform 1, when overexpressed, stimulates growth of the breast adenocarcinoma cell line MCF-7. Isoform 2 has no effect on cell growth.[1] [2] [3]
Publication Abstract from PubMed
The RNA-binding protein Lin28 regulates the processing of a developmentally important group of microRNAs, the let-7 family. Lin28 blocks the biogenesis of let-7 in embryonic stem cells and thereby prevents differentiation. It was shown that both RNA-binding domains (RBDs) of this protein, the cold-shock domain (CSD) and the zinc-knuckle domain (ZKD) are indispensable for pri- or pre-let-7 binding and blocking its maturation. Here, we systematically examined the nucleic acid-binding preferences of the Lin28 RBDs and determined the crystal structure of the Lin28 CSD in the absence and presence of nucleic acids. Both RNA-binding domains bind to single-stranded nucleic acids with the ZKD mediating specific binding to a conserved GGAG motif and the CSD showing only limited sequence specificity. However, only the isolated Lin28 CSD, but not the ZKD, can bind with a reasonable affinity to pre-let-7 and thus is able to remodel the terminal loop of pre-let-7 including the Dicer cleavage site. Further mutagenesis studies reveal that the Lin28 CSD induces a conformational change in the terminal loop of pre-let-7 and thereby facilitates a subsequent specific binding of the Lin28 ZKD to the conserved GGAG motif.
The Lin28 cold-shock domain remodels pre-let-7 microRNA.,Mayr F, Schutz A, Doge N, Heinemann U Nucleic Acids Res. 2012 May 8. PMID:22570413[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Guo Y, Chen Y, Ito H, Watanabe A, Ge X, Kodama T, Aburatani H. Identification and characterization of lin-28 homolog B (LIN28B) in human hepatocellular carcinoma. Gene. 2006 Dec 15;384:51-61. Epub 2006 Jul 28. PMID:16971064 doi:http://dx.doi.org/S0378-1119(06)00444-6
- ↑ Heo I, Joo C, Cho J, Ha M, Han J, Kim VN. Lin28 mediates the terminal uridylation of let-7 precursor MicroRNA. Mol Cell. 2008 Oct 24;32(2):276-84. doi: 10.1016/j.molcel.2008.09.014. PMID:18951094 doi:http://dx.doi.org/10.1016/j.molcel.2008.09.014
- ↑ Heo I, Joo C, Kim YK, Ha M, Yoon MJ, Cho J, Yeom KH, Han J, Kim VN. TUT4 in concert with Lin28 suppresses microRNA biogenesis through pre-microRNA uridylation. Cell. 2009 Aug 21;138(4):696-708. doi: 10.1016/j.cell.2009.08.002. PMID:19703396 doi:http://dx.doi.org/10.1016/j.cell.2009.08.002
- ↑ Mayr F, Schutz A, Doge N, Heinemann U. The Lin28 cold-shock domain remodels pre-let-7 microRNA. Nucleic Acids Res. 2012 May 8. PMID:22570413 doi:10.1093/nar/gks355
