DCPS

DCPS Full Name

decapping enzyme, scavenger

DCPS Introduction

DCPS encodes the scavenger decapping enzyme, a small pyrophosphatase that performs a specialized but important clean-up function in the life cycle of messenger RNA. Whereas the enzyme DCP2 removes the cap from intact mRNAs to initiate their decay from the 5' end, the scavenger enzyme acts at the end of the opposite route of mRNA degradation, the 3'-to-5' pathway, in which transcripts are chewed backward from their tail. When a partially degraded mRNA is reduced to a short fragment that still carries the 5' cap, the scavenger decapping enzyme hydrolyzes the cap to release m7GMP, allowing the residual nucleotide to be recycled and preventing the accumulation of capped fragments that could otherwise interfere with cellular processes. DCPS is thus a housekeeping enzyme that maintains the pool of free cap nucleotides and completes the disposal of mRNA remnants. The enzyme is also unusual among decapping proteins in being able to hydrolyze caps on a variety of substrates, including small capped RNAs, and it operates both in the cytoplasm and in the nucleus. Interest in DCPS increased dramatically when inhibitors of the enzyme were found to improve the phenotype of mouse models of spinal muscular atrophy, a devastating motor neuron disease, because DCPS inhibition alters the metabolism of specific RNAs relevant to motor neuron survival. This unexpected connection has made DCPS both a subject of mechanistic research and a candidate drug target in neurodegeneration.

Figure 1. The structure of DCPS.

Pyrophosphatase Fold and Catalytic Mechanism
The scavenger decapping enzyme belongs to the histidine triad (HIT) family of nucleotide hydrolases, so named for a conserved His-X-His-X-His motif that forms the active site.
The enzyme adopts a homodimeric structure in which each subunit contributes residues to the active site, and the dimer interface is essential for catalytic activity.
DCPS cleaves the pyrophosphate bond of the cap structure, releasing m7GMP and leaving a 5'-monophosphate on the residual RNA fragment.
Unlike DCP2, which acts on long capped mRNAs, DCPS prefers short RNA substrates and can hydrolyze the cap from oligonucleotides as well as from certain small regulatory RNAs.
The DCPS gene is located on human chromosome 11, and the protein is expressed in most tissues, consistent with a general housekeeping role.
Within the cell, DCPS is found in both the cytoplasm and the nucleus, and its localization reflects the sites where capped RNA fragments are generated.
The enzyme requires magnesium ions for catalysis, and its activity is inhibited by nucleotide analogs that have been developed as pharmacological tools.

mRNA Decay Completion, Nucleotide Recycling, and Therapeutic Potential
In the 3'-to-5' mRNA decay pathway, the exosome degrades transcripts from their poly(A) tail, and DCPS completes the process by hydrolyzing the cap of the residual fragment so that its components can be recycled.
The enzyme also acts on the products of endonucleolytic cleavage, such as those generated during the degradation of mRNAs by the nonsense-mediated decay or by RNA interference pathways, ensuring that capped remnants do not accumulate.
Although DCPS is not essential for the bulk decay of intact mRNAs, its loss sensitizes cells to the accumulation of capped RNA fragments and compromises the efficient disposal of certain transcripts.
The discovery that small-molecule inhibitors of DCPS, originally developed as antiviral compounds, improve motor function and survival in mouse models of spinal muscular atrophy redirected attention to the enzyme as a potential therapeutic target in neurodegeneration.
Mechanistic studies suggest that DCPS inhibition alters the abundance of specific capped small RNAs and messenger RNAs in motor neurons, although the full pathway linking enzyme inhibition to neuroprotection remains to be defined.
The continued development of selective DCPS inhibitors, and the analysis of their effects on RNA metabolism in the nervous system, represents an active frontier at the interface of RNA biology and drug discovery.

Alternate Names for DCPS

DCPS; decapping enzyme, scavenger; scavenger mRNA-decapping enzyme DcpS; HINT 5; HSL1; HSPC015; DCS-1; mRNA decapping enzyme; heat shock-like protein 1; histidine triad protein member 5; hint-related 7meGMP-directed hydrolase; homolog of C. elegans 7meGMP-directed hydrolase dcs-1; HINT-5;