mRNA decapping enzyme Dcp1p
Saccharomyces cerevisiae (Baker's yeast)
Expression of genes from DNA to RNA (transcription) and then to proteins (translation) is a highly regulated process. It is regulated at various levels during transcription and translation. In eukaryotes, one of the ways of controlling gene expression involves the turnover or degradation of the messenger RNA (mRNA), preventing its translation to protein. mRNA degradation is also responsible for antiviral defenses and elimination of abnormal mRNA. One of the pathways of mRNA degradation involves the shortening of the poly(A) tail at the 3' end, also called deadenylation. This is followed by decapping, which involves the removal of the 5' end cap structure. The deadenylated and decapped mRNA is the digested by an enzyme that is a 5'-3' exonuclease, Xrn1p. Dcp1p is a protein that participates in the critical step of decapping. It acts in conjunction with Dcp2p, which is the catalytic subunit, as part of a decapping holoenzyme or complex.
The structure seen here is that of Dcp1p. It is composed of three alpha-helices and seven beta-strands in the form of a beta-sandwich of two antiparallel beta-sheets. The overall fold is very similar to the EVH1 family of protein domains, which recognize and bind proline-rich sequences (PRS). However, the presence of two extra alpha helices in Dcp1p indicates that Dcp1p may belong to a novel class of EVH1 domains. The molecular surface of Dcp1p shows two conserved patches. One of the patches is structurally analogous to the hotspot of disease mutations in the EVH1-domain of N-WASP. It is required for the decapping function of the Dcp1p-Dcp2p complex. The other conserved patch corresponds to the PRS-binding site of EVH1 domains. However, mutations in this patch do not affect decapping or complex formation with Dcp2p. Hence, the authors suggest it as a possible binding site for other regulatory decapping proteins. Dcp1p also has a conserved hydrophobic region between the two conserved patches which is critical for decapping.
Protein Data Bank (PDB)
She, M. Decker, C.J. Sundramurthy, K. Liu, Y. Chen, N. Parker, R. Song, H.; "Crystal structure of Dcp1p and its functional implications in mRNA decapping"; Nat.Struct.Mol.Biol.; (2004) 11:249-256 PubMed:14758354.
author: Ashwini Patil