The scavenger mRNA decapping enzyme DcpS is a member of the HIT family of pyrophosphatases

• Published in: The EMBO journal Vol. 21; no. 17; pp. 4699 - 4708
• Main Authors: Liu, Hudan, Rodgers, Nancy D., Jiao, Xinfu, Kiledjian, Megerditch
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 02.09.2002; Blackwell Publishing Ltd; Oxford University Press
• Subjects: Amino Acid Motifs; Caenorhabditis elegans Proteins - chemistry; decapping; DNA, Complementary - genetics; Drosophila Proteins - chemistry; Endoribonucleases - classification; Endoribonucleases - genetics; Endoribonucleases - isolation & purification; Endoribonucleases - physiology; HIT motif; Humans; mammalian mRNA turnover; Methylation; Molecular Weight; Multigene Family; Pyrophosphatases - classification; Recombinant Fusion Proteins - metabolism; RNA Caps - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Schizosaccharomyces pombe Proteins - chemistry; Sequence Alignment; Sequence Homology, Amino Acid; Species Specificity
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/cdf448

We recently demonstrated that the major decapping activity in mammalian cells involves DcpS, a scavenger pyrophosphatase that hydrolyzes the residual cap structure following 3′ to 5′ decay of an mRNA. The association of DcpS with 3′ to 5′ exonuclease exosome components suggests that these two activities are linked and there is a coupled exonucleolytic decay‐dependent decapping pathway. We purified DcpS from mammalian cells and identified the cDNA encoding a novel 40 kDa protein possessing DcpS activity. Consistent with purified DcpS, the recombinant protein specifically hydrolyzed methylated cap analog but did not hydrolyze unmethylated cap analog nor did it function on intact capped RNA. Sequence alignments of DcpS from different organisms revealed the presence of a conserved hexapeptide, containing a histidine triad (HIT) sequence with three histidines separated by hydrophobic residues. Mutagenesis analysis revealed that the central histidine within the DcpS HIT motif is critical for decapping activity and defines the HIT motif as a new mRNA decapping domain, making DcpS the first member of the HIT family of proteins with a defined biological function.