Role of FAST Kinase Domains 3 (FASTKD3) in Post-transcriptional Regulation of Mitochondrial Gene Expression

J Biol Chem. 2016 Dec 9;291(50):25877-25887. doi: 10.1074/jbc.M116.730291. Epub 2016 Oct 27.

Abstract

The Fas-activated serine/threonine kinase (FASTK) family of proteins has recently emerged as a central regulator of mitochondrial gene expression through the function of an unusual RNA-binding domain named RAP (for RNA-binding domain abundant in Apicomplexans), shared by all six members of the family. Here we describe the role of one of the less characterized members, FASTKD3, in mitochondrial RNA metabolism. First, we show that, in contrast to FASTK, FASTKD2, and FASTKD5, FASTKD3 does not localize in mitochondrial RNA granules, which are sites of processing and maturation of mtRNAs and ribosome biogenesis. Second, we generated FASTKD3 homozygous knock-out cell lines by homologous recombination and observed that the absence of FASTKD3 resulted in increased steady-state levels and half-lives of a subset of mature mitochondrial mRNAs: ND2, ND3, CYTB, COX2, and ATP8/6. No aberrant processing of RNA precursors was observed. Rescue experiments demonstrated that RAP domain is required for FASTKD3 function in mRNA stability. Besides, we describe that FASTKD3 is required for efficient COX1 mRNA translation without altering mRNA levels, which results in a decrease in the steady-state levels of COX1 protein. This finding is associated with reduced mitochondrial complex IV assembly and activity. Our observations suggest that the function of this family of proteins goes beyond RNA processing and ribosome assembly and includes RNA stability and translation regulation within mitochondria.

Keywords: FASTKD3; RNA; RNA metabolism; gene expression; mitochondria; post-transcriptional regulation; translation; translation control.

MeSH terms

  • Cell Line, Tumor
  • Cyclooxygenase 1 / biosynthesis
  • Cyclooxygenase 1 / genetics
  • Electron Transport Complex IV / biosynthesis
  • Electron Transport Complex IV / genetics
  • Gene Expression Regulation / physiology*
  • Humans
  • Mitochondria / genetics
  • Mitochondria / metabolism*
  • Mitochondrial Proteins / biosynthesis*
  • Mitochondrial Proteins / genetics
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA / genetics
  • RNA / metabolism*
  • RNA Stability
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism*
  • RNA, Mitochondrial

Substances

  • Mitochondrial Proteins
  • RNA, Messenger
  • RNA, Mitochondrial
  • RNA
  • Cyclooxygenase 1
  • PTGS1 protein, human
  • Electron Transport Complex IV
  • FASTKD3 protein, human
  • Protein-Serine-Threonine Kinases