Werner syndrome (WS) is a genetic premature aging disorder in which patients appear much older than their chronological age. The gene mutated in WS encodes a nuclear protein (WRN) which possesses 3'-5' exonuclease and ATPase-dependent 3'-5' helicase activities. The genomic instability associated with WS cells and the biochemical characteristics of WRN suggest that WRN plays a role in DNA metabolic pathways such as transcription, replication, recombination and repair. Recently we have identified poly(ADP-ribose) polymerase-1 (PARP-1) as a new WRN interacting protein. In this paper, we further mapped the interacting domains. We found that PARP-1 bound to the N-terminus of WRN and to the C-terminus containing the RecQ-conserved (RQC) domain. WRN bound to the N-terminus of PARP-1 containing DNA binding and BRCA1 C-terminal (BRCT) domains. We show that unmodified PARP-1 inhibited both WRN exonuclease and helicase activities, and to our knowledge is the only known WRN protein partner that inactivates both of the WRN's catalytic activities suggesting a biologically significant regulation. Moreover, this dual inhibition seems to be specific for PARP-1, as PARP-2 did not affect WRN helicase activity and only slightly inhibited WRN exonuclease activity. The differential effect of PARP-1 and PARP-2 on WRN catalytic activity was not due to differences in affinity for WRN or the DNA substrate. Finally, we demonstrate that the inhibition of WRN by PARP-1 was influenced by the poly(ADP-ribosyl)ation state of PARP-1. The biological relevance of the specific modulation of WRN catalytic activities by PARP-1 are discussed in the context of pathways in which these proteins may function together, namely in the repair of DNA strand breaks.

Journal Article Cloning and sequencing of POU-boxes expressed in Xenopus laevis neurula embryos Get access Mireille Baltzinger, Mireille Baltzinger Laboratoire de Biochimie, Institut de Biologie Moléculaire et Cellulaire du CNRS15 Rue René Descartes, 67084 Strasbourg Cedex, France Search for other works by this author on: Oxford Academic PubMed Google Scholar Patrick Stiegler, Patrick Stiegler Laboratoire de Biochimie, Institut de Biologie Moléculaire et Cellulaire du CNRS15 Rue René Descartes, 67084 Strasbourg Cedex, France Search for other works by this author on: Oxford Academic PubMed Google Scholar Pierre Remy Pierre Remy Laboratoire de Biochimie, Institut de Biologie Moléculaire et Cellulaire du CNRS15 Rue René Descartes, 67084 Strasbourg Cedex, France Search for other works by this author on: Oxford Academic PubMed Google Scholar Nucleic Acids Research, Volume 18, Issue 20, 25 October 1990, Page 6131, https://doi.org/10.1093/nar/18.20.6131 Published: 25 October 1990 Article history Received: 17 September 1990 Published: 25 October 1990

Antibodies directed against E. coli ribosomal protein S1 were used in immunoblotting assays to search for an S1-like protein in the ribosome of spinach chloroplast. An immunological cross-reaction was reproducibly detected on the blots and inhibition experiments have demonstrated its specificity. The chloroplastic ribosomal protein which has epitopes common to antigenic determinants of the E. coli protein S1 was identified as being protein S2/S3.

The ribosomes are multimolecular particles where protein synthesis takes place. This complex process is achieved through a coordinated interaction between the ribosomes and the macromolecules involved: mRNAs, tRNAs and translational factors. Understanding of the functional role of the ribosome requires detailed knowledge of its structure and of the spatial relationship between its constituent molecules. Despite the complexity of the its structure, the ribosome is the sub cellular particle where the largest amount of information is available, as the primary structure of the 3 RNAs and of the the 52 proteins of E.coli ribosome is completely determined.

The ribosomal RNAs play a fundamental role in ribosome structure and function. For a long time, only the structural function was considered: they represent the backbone around which the ribosomal proteins are assembled in the course of ribosome assembly. But more recently it appeared that they may also play a functional role, as several regions within the RNAs have been found to interact directly with the macromolecules involved in protein synthesis.