Priority Research Papers:
Cis-acting elements in its 3′ UTR mediate post-transcriptional regulation of KRAS
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Minlee Kim1,3, Nicole Kogan1,2 and Frank J. Slack3
1 Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
2 Current address: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
3 Institute for RNA Medicine, Department of Pathology, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA, USA
Frank J. Slack, email:
Keywords: KRAS, 3′ UTR, post-transcriptional regulation, microRNAs (miRNAs), miR-185
Received: August 20, 2015 Accepted: January 17, 2016 Published: February 22, 2016
Multiple RNA-binding proteins and non-coding RNAs, such as microRNAs (miRNAs), are involved in post-transcriptional gene regulation through recognition motifs in the 3′ untranslated region (UTR) of their target genes. The KRAS gene encodes a key signaling protein, and its messenger RNA (mRNA) contains an exceptionally long 3′ UTR; this suggests that it may be subject to a highly complex set of regulatory processes. However, 3′ UTR-dependent regulation of KRAS expression has not been explored in detail. Using extensive deletion and mutational analyses combined with luciferase reporter assays, we have identified inhibitory and stabilizing cis-acting regions within the KRAS 3′ UTR that may interact with miRNAs and RNA-binding proteins, such as HuR. Particularly, we have identified an AU-rich 49-nt fragment in the KRAS 3′ UTR that is required for KRAS 3′ UTR reporter repression. This element contains a miR-185 complementary element, and we show that overexpression of miR-185 represses endogenous KRAS mRNA and protein in vitro. In addition, we have identified another 49-nt fragment that is required to promote KRAS 3′ UTR reporter expression. These findings indicate that multiple cis-regulatory motifs in the 3′ UTR of KRAS finely modulate its expression, and sequence alterations within a binding motif may disrupt the precise functions of trans-regulatory factors, potentially leading to aberrant KRAS expression.
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