MUTATIONS IN THE AMINO-TERMINAL DOMAIN OF THE HUMAN POLY(ADP-RIBOSE) POLYMERASE THAT AFFECT ITS CATALYTIC ACTIVITY BUT NOT ITS DNA-BINDING CAPACITY

Poly-ADP ribosylation of nuclear proteins is activated when poly(ADP-r ibose) polymerase (PARP), a nuclear zinc-finger enzyme, binds to singl e-strand DNA breaks, To understand how the signal emerging from its DN A-binding domain (DBD) bound to such breaks is transduced to its catal ytic domain, the structure-function relationship of the DBD was invest igated, We have used mutagenesis by the polymerase chain reaction (PCR ) to generate a random library of PARP mutants, In this work, we descr ibe the identification of catalytically inactive mutants bearing singl e point mutations, located outside the two zinc fingers in the DBD, th at have conserved their full capacity to bind DNA. The results obtaine d demonstrate that the DNA-dependent activation of PARP requires not o nly a capacity to bind DNA but also a number of crucial residues to ma intain a conformation of the domain necessary to transfer an 'activati on signal' to the catalytic domain.