A transcribed pseudogene of MYLK promotes cell proliferation

• Published in: The FASEB journal Vol. 25; no. 7; p. 2305
• Main Authors: Han, Yoo Jeong, Ma, Shwu Fan, Yourek, Gregory, Park, Yoon-Dong, Garcia, Joe G N
• Format: Journal Article
• Language: English
• Published: United States 01.07.2011
• Subjects: Amino Acid Sequence; Base Sequence; Blotting, Western; Cell Line; Cell Line, Tumor; Cell Proliferation; Cells, Cultured; Chromosome Mapping; Chromosomes, Human, Pair 3 - genetics; Female; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Humans; Luciferases - genetics; Luciferases - metabolism; Molecular Sequence Data; Myosin-Light-Chain Kinase - genetics; Myosin-Light-Chain Kinase - metabolism; Promoter Regions, Genetic - genetics; Pseudogenes - genetics; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid; Sequence Homology, Nucleic Acid; Transcription, Genetic
• ISSN: 1530-6860
• DOI: 10.1096/fj.10-177808

Pseudogenes are considered nonfunctional genomic artifacts of catastrophic pathways. Recent evidence, however, indicates novel roles for pseudogenes as regulators of gene expression. We tested the functionality of myosin light chain kinase pseudogene (MYLKP1) in human cells and tissues by RT-PCR, promoter activity, and cell proliferation assays. MYLKP1 is partially duplicated from the original MYLK gene that encodes nonmuscle and smooth muscle myosin light chain kinase (smMLCK) isoforms and regulates cell contractility and cytokinesis. Despite strong homology with the smMLCK promoter (∼ 89.9%), the MYLKP1 promoter is minimally active in normal bronchial epithelial cells but highly active in lung adenocarcinoma cells. Moreover, MYLKP1 and smMLCK exhibit negatively correlated transcriptional patterns in normal and cancer cells with MYLKP1 strongly expressed in cancer cells and smMLCK highly expressed in non-neoplastic cells. For instance, expression of smMLCK decreased (19.5 ± 4.7 fold) in colon carcinoma tissues compared to normal colon tissues. Mechanistically, MYLKP1 overexpression inhibits smMLCK expression in cancer cells by decreasing RNA stability, leading to increased cell proliferation. These studies provide strong evidence for the functional involvement of pseudogenes in carcinogenesis and suggest MYLKP1 as a potential novel diagnostic or therapeutic target in human cancers.