Cis -acting elements in its 3′ UTR mediate post-transcriptional regulation of KRAS

• Published in: Oncotarget Vol. 7; no. 11; pp. 11770 - 11784
• Main Authors: Kim, Minlee, Kogan, Nicole, Slack, Frank J.
• Format: Journal Article
• Language: English
• Published: United States Impact Journals LLC 15.03.2016
• Subjects: 3' Untranslated Regions - genetics; Base Sequence; Gene Expression Regulation, Neoplastic; Genes, Reporter; Humans; Neoplasms - genetics; Priority Research Paper; Promoter Regions, Genetic; Proto-Oncogene Proteins p21(ras) - genetics; Regulatory Sequences, Nucleic Acid; RNA Processing, Post-Transcriptional; Tumor Cells, Cultured; KRAS; miR-185; 3′ UTR; post-transcriptional regulation; microRNAs (miRNAs)
• ISSN: 1949-2553; 1949-2553
• DOI: 10.18632/oncotarget.7599

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.