We isolated several clones from a matchmaker twohybrid system human lymphocyte cDNA library using an automodification domain of poly(ADP-ribose) synthetase (PARS) as a probe. A DNA sequence (V1 kbp) of the clone was identical to part of the Oct-1 DNA sequence. We then constructed either a His-tagged or GST fusion protein of the inserted cDNA from the clone and the fusion protein was shown to interact with PARS by far-Western blot analysis and coprecipitation with affinity resin. Furthermore, the His-tagged Oct-1/POU-homeo fusion protein interacted weakly with the octamer motif of the DRa promoter and the addition of PARS fusion protein greatly increased the DNA binding activity. These results suggest that PARS interacts with Oct-1 and stabilizes the binding of Oct-1 to the octamer motif.z 1998 Federation of European Biochemical Societies.
We screened a human lymphocyte cDNA library using the yeast two-hybrid system and an automodification domain of PARP as a probe. The DNA sequence of an isolated clone (clone 3-9) was identical to the partial cDNA sequence of the human ribosomal protein S3a. We confirmed that PARP interacts with clone 3-9 by performing binding studies using a GST-3-9 fusion protein as bait. We also demonstrated that native S3a in nuclear extracts of HL-60 cells interacts with the automodification domain of PARP and that PARP from nuclear extracts is coprecipitated with the GST-3-9 fusion protein. Furthermore, we demonstrated that Bcl-2 interacts with PARP in association with S3a and that the interaction of S3a and Bcl-2 with PARP causes a significant decrease in PARP activity. Since Bcl-2 failed to inhibit PARP activity in the absence of S3a, we suggest that Bcl-2 together with S3a prevents apoptosis probably by inhibiting PARP activity.
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