Poly ated proteins

Genomic sequence analysis has identified 17 structurally related proteins containing a PARP catalytic domain [3] however, closer inspection suggests that only PARPs 1-3, PARP-4 (vault PARP), and tankyrases 1 and 2 may truly function as poly(ADP-ribosyl)ating proteins. The remaining... 

It is important to identify each of the poly(ADP-ribosyI)ated proteins in order to clarify the role of poly(ADP-ribosyl)ation. Indeed we have identified some proteins that are poly(ADP-ribosyl)ated in the centrosome. One of these proteins is the tumor suppressor protein p33. p33 is a well known guardian of the genome, and it is essential for DNA repair and apoptosis. Interestingly, p33 also localizes to the centrosome and r ubites centrosome fonaion directly or indirectly. Our study revealed that inhibition of poly(ADP-ribosyl)arion of p33 due to administration of a PARP inhibitor or loss of PARP-1 mi t be involved in the defect in centrosome function and chromosomal instability. 

Since the conditions described above, i.e., intermitotic arrest, proliferation, and DNA damage are associated with dramatic changes in nucleotide pools, we conducted a study to determine the effect of nucleotides and their components on protein acceptors for poly(ADP-ribosyl)ation [11, 12]. Figure 1 shows the effect of increasing concentrations of Ap4A on poly(ADP-ribosyl)ated proteins in human lymphocytes. In the absence of Ap4A, the autoradiograph shows that the most prominent ADP-ribosylated proteins are poly(ADP-ribose) polymerase at mol. wt. 116,000, histone H-1 at 32,000,... 

Furthermore, some of our preliminary studies indicate that the turnover of poly-(ADP-ribosyl)ated proteins on polynucleosomes leads in time to an extensive modification of histone H2B. Thus, it is conceivable that during DNA repair in vivo, histone H2B modification results in destabilization of condensed chromatin and thereby permits increased accessibility to repair enzymes. Similarly, in active chromatin, where HI levels are greatly reduced, the damaged DNA might be more accessible to repair enzymes because of histone H2B hyper(ADP-ribosyl)ation. 

Gaudreau A, Menard L, de Murcia G, Poirier GG (submitted) Differential turnover of poly (ADP-ribosyl)ated proteins on polynucleosomes by poly (ADP-ribose) gly cohydrolase... 

Fig. 3. Comparison of poly(ADP-ribosyl)ated proteins isolated from E63 muscle cells and a nonfusing variant (Nf-1). Lane 1) prefusion E63 myoblasts (5 days) 2) differentiated E63 cells (8 days) lane 3) Nf-1 cells maintained for 8 days in culture...

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. 

It is evident that the area of water-soluble polymer covets a multitude of appHcations and encompasses a broad spectmm of compositions. Proteins (qv) and other biological materials ate coveted elsewhere in the Eniyclopedia. One of the products of this type, poly(aspartic acid), may be developed into interesting biodegradable commercial appHcations (70,71). 

Saxena A, Saffery R, Wong L, Kahtsis P, Choo KHA (2002a) Centromere proteins Cenpa, Cenpb, and Bub3 interact with Poly(ADP-ribose) Polymerase-1 protein and are poly(ADP-ribosyl)ated. J Biol... 

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.

Out data show that there are many proteins that arc poly(ADP-ribosyl)ated. In view of the dynamic process of poly(ADP-ribosyl)ation, a posttranslational modification undergoing rapid turnover, the recent discovery that poly(ADP-ribose) glycohydrolase (PARC) is also localized in the centrosome durii the cell cycle is very interesting and plausible. 

Identification of the poly(ADP-ribosyl)ated centrosomal proteins and clarification of the changes in subcellular localization by possible shutding between the centrosome and the nucleus will be essential for further understanding the role of poly(ADP-ribosyl)ation. It would also be very interesting to know the trigger(s) of poly(ADP-ribosyl)ation in the centrosome, since it is believed that this structure is devoid of DNA. Such analyses would clarify a novel mechanism of the regulation of the centrosome function by posttranslational poly(ADP-ribosyl)ation. 

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