C-terminal deadenylase domain of CCR4 and related domains
This subfamily contains the C-terminal catalytic domain of the deadenylases, Saccharomyces cerevisiae Ccr4p and two vertebrate homologs (CCR4a and CCR4b), and related domains. CCR4 belongs to the large EEP (exonuclease/endonuclease/phosphatase) superfamily that contains functionally diverse enzymes that share a common catalytic mechanism of cleaving phosphodiester bonds. CCR4 is the major deadenylase subunit of the CCR4-NOT transcription complex, which contains two deadenylase subunits and several noncatalytic subunits. The other deadenylase subunit, Caf1 (called Pop2 in yeast), is a DEDD-type protein and does not belong in this superfamily. Saccharomyces cerevisiae CCR4 (or Ccr4p) is a 3'-5' poly(A) RNA and ssDNA exonuclease. It is the catalytic subunit of the yeast mRNA deadenylase (Ccr4p/Pop2p/Not complex). This complex participates in various ways in mRNA metabolism, including transcription initiation and elongation, and mRNA degradation. Ccr4p degrades both poly(A) and single-stranded DNA. There are two vertebrate homologs of Ccr4p, CCR4a (also called CCR4-NOT transcription complex subunit 6 or CNOT6) and CCR4b (also called CNOT6-like or CNOT6L), which independently associate with other components to form distinct CCR4-NOT multisubunit complexes. The nuclease domain of CNOT6 and CNOT6L exhibits Mg2+-dependent deadenylase activity, with specificity for poly (A) RNA as substrate. CCR4a is a component of P-bodies and is necessary for foci formation. CCR4b regulates p27/Kip1 mRNA levels, thereby influencing cell cycle progression. They both contribute to the prevention of cell death by regulating insulin-like growth factor-binding protein 5.
Jiyao W et al.(2023). "The conserved domain database in 2023.",