BACKGROUND: The yeast yCCR4 factor belongs to the CCR4-NOT transcriptional 
regulatory complex, in which it interacts, through its leucine-rich repeat (LRR) 
motif with yPOP2. Recently, yCCR4 was shown to be a component of the major 
cytoplasmic mRNA deadenylase complex, and to contain a fold related to the 
Mg2+-dependent endonuclease core.
RESULTS: Here, we report the identification of nineteen yCCR4-related proteins 
in eukaryotes (including yeast, plants and animals), which all contain the yCCR4 
endonuclease-like fold, with highly conserved CCR4-specific residues. 
Phylogenetic and genomic analyses show that they form four distinct families, 
one of which contains the yCCR4 orthologs. The orthologs in animals possess a 
leucine-rich repeat domain. We show, using two-hybrid and far-Western assays, 
that the human member binds to the human yPOP2 homologs, i.e. hCAF1 and hPOP2, 
in a LRR-dependent manner.
CONCLUSIONS: We have identified the mammalian orthologs of yCCR4 and have shown 
that the human member binds to the human yPOP2 homologs, thus strongly 
suggesting conservation of the CCR4-NOT complex from yeast to human. All members 
of the four identified yCCR4-related protein families show stricking 
conservation of the endonuclease-like catalytic motifs of the yCCR4 C-terminal 
domain and therefore constitute a new family of potential deadenylases in 
mammals.