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C-terminal deadenylase domain of CCR4, nocturnin, and related domains This family contains the C-terminal catalytic domains of the deadenylases, CCR4 and nocturnin, and related domains. Nocturnin is a poly(A)-specific 3' exonuclease that specifically degrades the 3' poly(A) tail of RNA in a process known as deadenylation. This nuclease activity is manganese dependent. Nocturnin is expressed in the cytoplasm of the Xenopus laevis retinal photoreceptor cells in a rhythmic fashion, and it has been proposed that it participates in posttranscriptional regulation of the circadian clock or its outputs, and that the mRNA target(s) of this deadenylase are circadian clock-related. Saccharomyces cerevisiae 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. The deadenylase activities of Ccr4p and nocturnin differ: nocturnin degrades poly(A), Ccr4p degrades both poly(A) and single-stranded DNA, and in contrast to Ccr4p, nocturnin appears to function in a highly processive manner. This family belongs to the large EEP (exonuclease/endonuclease/phosphatase) superfamily that contains functionally diverse enzymes that share a common catalytic mechanism of cleaving phosphodiester bonds. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",