Faculty Bibliography

The histone methyltransferase PR-Set7/Set8 is the sole enzyme that catalyzes monomethylation of histone H4 at K20 (H4K20me1). Previous reports document disparate evidence regarding PR-Set7 expression during the cell cycle, the biological relevance of PR-Set7 interaction with PCNA, and its role in the cell. We find that PR-Set7 is indeed undetectable during S phase and instead is detected during late G2, mitosis, and early G1. PR-Set7 is transiently recruited to laser-induced DNA damage sites through its interaction with PCNA, after which 53BP1 is recruited dependent on PR-Set7 catalytic activity. During the DNA damage response, PR-Set7 interaction with PCNA through a specialized 'PIP degron' domain targets it for PCNA-coupled CRL4(Cdt2)-dependent proteolysis. PR-Set7 mutant in its 'PIP degron' is now detectable during S phase, during which the mutant protein accumulates. Outside the chromatin context, Skp2 promotes PR-Set7 degradation as well. These findings demonstrate a stringent spatiotemporal control of PR-Set7 that is essential for preserving the genomic integrity of mammalian cells

The BTB/POZ transcriptional repressor and candidate oncogene BCL6 is frequently misregulated in B-cell lymphomas. The interface through which the BCL6 BTB domain mediates recruitment of the SMRT, NCoR and BCoR corepressors was recently identified. To determine the contribution of this interface to BCL6 transcriptional and biological properties, we generated a peptide that specifically binds BCL6 and blocks corepressor recruitment in vivo. This inhibitor disrupts BCL6-mediated repression and establishment of silenced chromatin, reactivates natural BCL6 target genes, and abrogates BCL6 biological function in B cells. In BCL6-positive lymphoma cells, peptide blockade caused apoptosis and cell cycle arrest. BTB domain peptide inhibitors may constitute a novel therapeutic agent for B-cell lymphomas.

BACKGROUND:Ovarian dysplasia, a potential precursor to ovarian carcinoma, has been described in ovarian tissue obtained by prophylactic oophorectomy and also adjacent to ovarian carcinoma. Women with a family history of ovarian carcinoma, especially those of Jewish Ashkenazi descent, often test positive for BRCA mutant genes. Prophylactically removed ovaries, generally described as normal on macroscopic examination, can exhibit a "preneoplastic phenotype" and unsuspected neoplasm. METHODS:Histologic slides of ovarian tissue from 54 Ashkenazi Jewish women were reviewed. All had a family history of ovarian carcinoma and all were tested for BRCA mutations. Forty-four women tested positive. Thirty-one women underwent prophylactic oophorectomy and 23 underwent oophorectomy for ovarian carcinoma. Normal, dysplastic, and ovarian carcinoma epithelial cells were analyzed morphometrically combining nuclear area measurements with chromatin texture assessment using a novel method based on the computation of autocorrelation coefficients and a derived parameter (Beta). Discriminant analysis between classificatory algorithms was used to obtain results. RESULTS:Ovarian dysplasia was identified in 77.6% of the prophylactic oophorectomy specimens. An unsuspected ovarian carcinoma was diagnosed in one prophylactic oophorectomy specimen. Of 10 women who underwent prophylactic oophorectomy and were negative for BRCA mutations, three had ovarian dysplasia. The average nuclear measurements of the dysplastic cells were similar to those published previously. The new autocorrelation-based method evaluating nuclear texture, as revealed by tridimensional surface plots, demonstrated high discriminatory potential. Discriminant analysis based on nuclear area and nuclear texture information resulted in the correct classification of nearly all the cases in the three diagnostic categories. CONCLUSIONS:Ovaries removed by prophylactic oophorectomy examined in their entirety often reveal ovarian dysplasia and occasionally ovarian carcinoma. The new morphometric method used was highly discriminatory in the evaluation of nuclear texture. Ovarian dysplasia in women with risk factors for ovarian carcinoma is significant in early ovarian carcinogenesis.