RNA interference (RNAi) plays an important role in development, post-transcriptional regulation of gene expression in plants and animals and can impact genome organization and chromatin structure. While many studies focus on the identification of microRNA (miRNA) targets and the various downstream mechanisms of gene silencing, here we are interested in the regulation of a particular miRNA, let-7. The pluripotency factor Lin28 inhibits the biogenesis of the let-7 family of mammalian microRNAs. Lin28 is highly expressed in embryonic stem cells and has a fundamental role in regulation of development, glucose metabolism and tissue regeneration. Alternatively, Lin28 overexpression is correlated with the onset of numerous cancers, while let-7, a tumor suppressor, silences several human oncogenes. The Lin28/let-7 pathway is like a bistable switch. Each molecule represses expression of the other, and once the cell changes its state, the result is differentiation, or if the switch is reversed, cancer. At t h e molecular l e e l , Lin28 binds to precursor let-7 (pre-let-7) hairpins, triggering the 3' oligouridylation activity of TUT4 and/or TUT7. The oligoU tail added to pre-let-7 serves as a decay signal, as it is rapidly degraded by the exonuclease Dis3L2. In somatic cells, in the absence of L i n 2 8 , TUT4/7 promotes let-7 biogenesis by catalyzing single uridine addition to a subset of pre-let-7 miRNAs. Here, we propose to study the molecular basis of Lin28 mediated recruitment of TUT4/7 to pre-let-7, the switch in TUT4/7 activity between a monouridylase in the absence of Lin28 and an oligouridylase in the presence of Lin28, and the subsequent degradation of pre-let-7 by Dis3L2. We will utilize a similar approach to initiate an understanding of the broader role of TUT4/7 in marking both miRNA and mRNA with untemplated uridines.

Public Health Relevance

RNA interference (RNAi) plays an important role in development, the post-transcriptional regulation of gene expression in plants and animals and can impact genome organization and chromatin structure. While many studies focus on the identification of microRNA (miRNA) targets and the various downstream mechanisms of gene silencing, here we are interested in the regulation of a particular miRNA, let-7. Recently, it has been shown that the regulatory factors that control let-7 biogenesis were specifically linked to liver and colorectal cancer as wel as kidney cancer - Wilms' tumors and Perlman syndrome.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM114147-01A1
Application #
9027441
Study Section
Molecular Genetics A Study Section (MGA)
Program Officer
Bender, Michael T
Project Start
2016-06-10
Project End
2020-03-31
Budget Start
2016-06-10
Budget End
2017-03-31
Support Year
1
Fiscal Year
2016
Total Cost
$345,600
Indirect Cost
$165,600
Name
Cold Spring Harbor Laboratory
Department
Type
DUNS #
065968786
City
Cold Spring Harbor
State
NY
Country
United States
Zip Code
11724
Faehnle, Christopher R; Walleshauser, Jack; Joshua-Tor, Leemor (2017) Multi-domain utilization by TUT4 and TUT7 in control of let-7 biogenesis. Nat Struct Mol Biol 24:658-665