Protein methyltransferases PRMTs

Histone methylation by methyltransferases is another vddely described modification that also plays an important role in regulation of transcriptional activity. Methylation can occur either on arginine or on lysine residues in the N-termini of histones and therefore this group of enzymes can be separated into protein arginine methyltransferases (PRMTs) and lysine methyltransferases (KMTs). 

Histone methylation participates in the regulation of gene expression patterns. Unlike histone acetylation, histone methylation does not alter the charge of the amino acid and hence the histone tail. There are changes in the basicity and the hydrophobicity which are relatively small when viewed at the scale of the histone but still influence the affinity of the histone tails to certain proteins, for example transcription factors, which in turn result in certain signaling events. The histone methyltransferases are usually subdivided into three classes SET domain lysine methyltransfeases, nonSET domain lysine methyltransferases and arginine methyltransferases (PRMTs). All of them utilize S-adenosylmethionine (SAM) as cosubstrate for the methylation reaction... 

Similarly, histone arginine/lysine methylation can be the target for the development of therapeutics. The status of histone arginine methylation is intimately involved in gene transcription. Recently, several compounds were found to inhibit protein arginine methyltransferases (PRMTs) [54]. It can also be interesting to explore how this small molecule could be exploited for developing therapeutics. 

Fig. 7. Sequence alignment of known protein arginine methyltransferases (PRMTs). Sequences essential for AdoMet and substrate binding are indicated by blue and red bars. (See Color Insert.)...

Arginine methylation is catalysed by protein arginine methyltransferases (PRMTs, EC number 2.1.1.125), and thus far eight human PRMTs have been identified, with several more putative enzymes predicted. Two subclasses of PRMTs exist Class I PRMTs catalyse asymmetric dimethylation, while Class II PRMTs catalyse symmetric dimethylation of arginine. All three methyl-transferase subfamilies (SET-domain KMTs, DOTIL and PRMTs) utilise S-adenosylmethionine as an electrophilic methyl source. 

Histone deacetylases (HDACs), histone acetyltransferases (HMTs), histone demethylases (HDMTs), protein arginine methyltransterases (PRMTs), histone arginine demethylases (HADs), and DNA methyltransferases (DNMTs). 

PRMT Protein Arg(R) methyltransferase, catalyzes the transfer of methyl group from S-adenosylmethionine to the... 

The identities of several protein arginine methyltransferases are now known, but only a few have been shown to have specificity for histone proteins. The mammalian PRMT1, JBP1, and CARMI, as well as the Saccharomyces Rmtl, have histone methyltransferase activity (McBride and Silver, 2001). However, the catalytic mechanism for the methyl group transfer as well as the makeup of the active sites of PRMTs differ somewhat from SET domain proteins. 

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