LIN28B
Description
The LIN28B (lin-28 homolog B) is a protein-coding gene located on chromosome 6.
LIN28B is a protein that inhibits the production of microRNAs (miRNAs), particularly let-7 and potentially others like miR107, miR-143, and miR-200c. It does this by binding to primary let-7 transcripts (pri-let-7) and sequestering them in the nucleolus, away from the microprocessor complex. This prevents the processing of pri-let-7 into mature let-7 miRNA. Importantly, LIN28B does not affect the processing of pri-miR21. The repression of let-7 expression is essential for normal development and contributes to maintaining the pluripotent state of embryonic stem cells by preventing let-7-mediated differentiation. When present in excess, LIN28B recruits ZCCHC11/TUT4 uridylyltransferase to pre-let-7 transcripts, leading to their terminal uridylation and subsequent degradation. However, this activity might not be relevant in living organisms, as LIN28B-mediated inhibition of let-7 miRNA maturation seems to be independent of ZCCHC11. The interaction between LIN28B and target pre-miRNAs occurs through a 5'-GGAG-3' motif located in the terminal loop of the pre-miRNA. LIN28B is also involved in MYC-induced let-7 repression, though this is based on similar mechanisms. When overexpressed, isoform 1 of LIN28B stimulates growth in the breast adenocarcinoma cell line MCF-7. However, isoform 2 has no effect on cell growth.
LIN28B is also known as CSDD2.
