Poly ated proteins degradation

It appears from our results that free mRNP possesses both the enzymatic activities of synthesis and degradation of poly(ADP-ribose). A cytoplasmic poly(ADP-ribose) glycohydrolase has also recently been described by Tanuma et al. (12). ITiis suggests a balance between the ADP-ribosylation/de-ADP-ribosylation states of free mRNP proteins. In addition, free mRNP poly(ADP-ribosyl)ated proteins seem associated with different ribonucleoprotein particles which are removed from free mRNP by a 0.5 M KCl treatment. It is noteworthy that low rnoLwt. RNA able to inhibit mRNA translation in vitro have been isolated from such ribonucleoprotein particles (13). Free mRNP proteins have also been suggested to play a role in the mechanisms and regulation of the translation of mRNA (7, 8). One could speculate a role of poly(ADP-ribosyl)ation in the stmctural changes that may occur in the free mRNP to permit the translation of the mRNA repressed in these particles. 

Figure 1. Metabolism of poly(ADP-ribose). Poly(ADP-ribosyl)ation is a posttranslational modification of acceptor proteins, and poly(ADP-ribose) itself serves as a component of cell struaure. Poly(ADP-ribose) glycohydrolase (PARC) is a main enzyme to degrade poly(ADP-ribose) and forms ADP-ribose as product. Other degrading enzymes ate phosphodiesterase (or pyrophosphatase) and ADP-ribosyl protein lyase.

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