Discoveries in Yeast
CCR4-NOT is a general transcription regulatory complex in yeast that is found to be associated with mRNA metabolism, transcription initiation, and mRNA degradation. CCR4 has been found to contain RNA and single-stranded DNA 3’to 5’ exonuclease activities. Another component associated with the CCR4 complex is CAF1 protein, which has been found to contain 3’to 5’ or 5’ to 3’ exonuclease domains in Mus musculus and Caenorhabditis elegans. This protein has not been found in yeast, which suggests that it is likely to have an abnormal exonuclease domain like the one seen in a metazoan. Yeast contains Rat1 and Xrn1 exonuclease. The Rat1 works just like the human type (Xrn2) and Xrn1 function in the cytoplasm is in the 5’ to 3’ direction to degrade RNAs (pre-5.8s and 25s rRNAs) in the absence of Rat1.
Read more about this topic: Exonuclease
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