Overview on ADP ribosylation and PARP superfamily of proteins.

In 1963, the team led by Pierre Chambon described the synthesis of poly(ADP-ribose) (PAR). ADP-ribosylation is a reversible post-translational modification used by PARP-domain proteins sharing a NAD+ binding pocket, that modify protein targets. It consists in mono ADP-ribose (MAR) or multiple ADP-ribose subunits (PAR). PARylation was then studied either in plants (Miwa et al. 1975), as well as in animals (Sugimura 1973, Miwa et al. 1973, Hayaishi and Ueda 1977). However, only starting from 1995 plant PARPs were studied at molecular and biochemical level (Lepiniec et al., 1995, Berglund et al., 1996, Babiychuk et al., 1998). Recently, two groups have analysed the PARP superfamily of proteins (Citarelli et al., 2010, Perina et al., 2014) whilst the Kangasjarvi team updated the phylogenetic tree focusing particularly on PARP domain containing SRO (Similar to RCD One) like proteins, such as Radical-Induced Cell Death1 (RCD1) (Jaspers et al., 2010). A tight collaboration between Japanese and Italian teams working on PARP and PAR was started since 1985 by Hisanori Suzuki, professor of Chemical Biology at Verona University. Following jointed efforts, in 1997 an Italy-Japan bilateral seminar on ADP-ribosylation was organised in Kyoto, with chairman Kunihiro Ueda, a pioneer of ADP-ribose studies. This special issue wants to acknowledge these efforts, that made possible not only to advance the studies on PARPs but also to tighten personal friendships. This topic on PARP superfamily and proteins binding or degrading PAR intercepts a new wave of interest and revival on the topics on PAR.