Journal
CELL DEATH AND DIFFERENTIATION
Volume 20, Issue 3, Pages 430-442Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/cdd.2012.135
Keywords
miR-125b; spindle assembly checkpoint; MAD1; apoptosis; mitotic delay; chromosomal abnormalities
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Funding
- Department of Biotechnology [BT/PR/5524/Med/14/649/2004, BT/01/COE/05/04]
- Council of Scientific and Industrial Research [IAP 001]
- University Grants Commission (New Delhi, India)
- Council of Scientific and Industrial Research (New Delhi, India)
- Department of Atomic Energy (Mumbai, India)
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The spindle assembly checkpoint (SAC) is a 'wait-anaphase' mechanism that has evolved in eukaryotic cells in response to the stochastic nature of chromosome-spindle attachments. In the recent past, different aspects of the SAC regulation have been described. However, the role of microRNAs in the SAC is vaguely understood. We report here that Mad1, a core SAC protein, is repressed by human miR-125b. Mad1 serves as an adaptor protein for Mad2 - which functions to inhibit anaphase entry till the chromosomal defects in metaphase are corrected. We show that exogenous expression of miR-125b, through downregulation of Mad1, delays cells at metaphase. As a result of this delay, cells proceed towards apoptotic death, which follows from elevated chromosomal abnormalities upon ectopic expression of miR-125b. Moreover, expressions of Mad1 and miR-125b are inversely correlated in a variety of cancer cell lines, as well as in primary head and neck tumour tissues. We conclude that increased expression of miR-125b inhibits cell proliferation by suppressing Mad1 and activating the SAC transiently. We hypothesize an optimum Mad1 level and thus, a properly scheduled SAC is maintained partly by miR-125b. Cell Death and Differentiation (2013) 20, 430-442; doi:10.1038/cdd.2012.135; published online 26 October 2012
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