The BRCA1-associated protein BARD1 is a putative tumor suppressor. We suggest that BARD1 is a mediator of apoptosis since (1) cell death in vivo (ischemic stroke) and in vitro is accompanied by increased levels of BARD1 protein and mRNA; (2) overexpression of BARD1 induces cell death with all features of apoptosis; and (3) BARD1-repressed cells are defective for the apoptotic response to genotoxic stress. The proapoptotic activity of BARD1 involves binding to and elevations of p53. BRCA1 is not required for but partially counteracts apoptosis induction by BARD1. A tumor-associated mutation Q564H of BARD1 is defective in apoptosis induction, thus suggesting a role of BARD1 in tumor suppression by mediating the signaling from proapoptotic stress toward induction of apoptosis.

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Subcellular fractionation studies have shown that the thymidine (dT) kinases induced by vaccinia and herpes simplex type I ( H S V-I) viruses dT kinase-deficient HeLa (BU25) and L M ( TK-) cells. These analyses revealed that the sedimentation coefficients of the vaccinia and HSV-I induced dT kinases were similar to those of the HeLa S3 and L M cytosol enzymes, but the viralinduced dT kinases exhibited greater disc PAGE mobilities ( R m values) and lower p l values than the HeLa S3 and L M cytosol dT kinases. The vaccinia and HSV-I induced dT kinases were distinctly different. Both viral-induced enzymes also differed from L M ( T K -) mitochondrial dT kinase in sedimentation coefficient, R m and PI. Small differences were found between the H S V-I induced dT kinase and a human mitochondrialspecific isozyme. However, the HS V-1 induced dT kinase resembled the mitochondrialspecific human and mouse dT kinases in ability to

Pituitary adenylate cyclase-activating-polypeptide (PACAP) is a new member of the secretin/glucagon/vasoactive intestinal peptide family of peptides; it occurs as two amidated forms with 38 (PACAP38) and 27 (PACAP27) amino acids. Rabbit antisera against synthetic PACAP27 were characterized by enzyme-linked immunosorbent assay. One of the antisera, using a high antibody titer, recognized both PACAP27 and PACAP38 and was found useful for immunohistochemistry. The distribution and ultrastructural localization of PACAP-like immunoreactivity (PACAP-LI) in the rat testes at different stages of spermatogenesis were studied with this antiserum. Four oligonucleotide probes, each complementary to a different region covering a different intron-exon junction, were chosen to maximize hybridization based on the predicted secondary structure of PACAP messenger RNA. PACAP-LI was detected in the developing germ cells but not in either Sertoli or Leydig cells. Intense PACAP-LI was found in spermatids situated near the lumen of the seminiferous tubules. Lower levels of PACAP-LI were detected in spermatogonia and primary spermatocytes, but no PACAP-LI was found in mature spermatids, testicular spermatozoa, or epididymal spermatozoa. In spermatids, PACAP-LI was detected during the cap phase and acrosome phase but not in the maturation phase. At the ultrastructural level, numerous gold particles representing PACAP-LI were found in both acrosomal granules and acrosomal caps of spermatids, while a few particles were found in the Golgi complex. Very few gold particles were seen in the acrosome of mature spermatids and spermatozoa. PACAP-LI decreased and finally disappeared from spermatids during the late developmental stages. In situ hybridization indicated that most of the signal was detected near the perimeter of seminiferous tubules in early developing germ cells, especially in spermatogonia and primary spermatocytes, suggesting that transcription of the PACAP gene occurs in spermatogonia and primary spermatocytes. The processing of the prohormone appears to be slow, and mature PACAP only appears in spermatids. These morphological findings suggest that PACAP-like substances, synthesized by germ cells, participate in spermatogenesis, particularly spermiogenesis, probably by an autocrine and paracrine mechanism. However, the possibility that PACAP acts on the Sertoli and/or Leydig cells cannot be excluded.

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Biochemical and immui~olo~ical experiments have been performed to learn whether human and avian herpesvirus-induced d T kinases could be distinguished from the cytosol and mitochondrial d T kinase isozymes of uninfected cells. The dT kinases itiduced by human herpes simplex virus types I and 2 ( H S V-I and HSV-2) and by avian infectious laryngotracheitis virus ( I L T V ) and herpesvirus of turkeys ( H V T ) were kinases oj uninfected cells with respect to sedimentation coeficients and sensitivity to dCTP inhibition; and ( 3 ) HSV-I-and HSV-2-induced dT kinases differ from human cytosol and mitochondrial dT kinases in thermal lability and antigenic determinants. The cellular and the viral-induced d T kinase isozymes were all inhibited by the end product inhibitor, dTTP. Immunoglobulin ( l g ) from sera of rabbits immunized with the HS V-I-induced dTkinase inhibited the homologous enzyme and some anti-type 1 Ig preparations partial1.v inhibited the H S V-2 d T kinase, but the anti-type I Ig inhibited neither cytosol and mitochondrial d T kinases from human, mouse, and monkey cells, nor the d T kinases induced by ILTV, H V T , or vaccinia virus. Anti-type 2 Ig inhibited the homologous HSV-2 d T kinase, but not HSV-I or human mitochondria1 d T kinase.Thymidine (dT) kinase activity is induced early after infection of cells by avian, porcine, simian and human herpesviruses (Buchan and Watson, 1969;Kit et al., 1967 Kit et al., , 1974a Kit et al., , e, 1975 Thouless, 1972). The herpesviruses-induced enzymes differ from the major cytosol d T kinases of host cells in biochemical, immunological and genetic properties, suggesting that they are virus-coded proteins. Hence, the herpesvirus-induced d T kinases are potentially useful markers for: ( I ) studies on the regulation of gene expression; and (2) the detection of virus genetic information in transformed cells and in tumors suspected of having been caused by herpes-viruses. To be useful for these purposes, however, the herpesvirus-induced d T kinases must also be distinguishable from the genetically distinct mitochondrial d T kinase of host cells (Kit and Leung, 1974a, b ; Kit et al., 1972Kit et al., , 1973Kit et al., , 1974d. Previous studies have shown that the human and avian herpesvirus-induced d T kinases have larger sedimentation coefficients than vertebrate mitochondrial d T kinases. They also differ from mouse mitochondrial d T kinase in electrophoretic mobility and isoelectric point. However, the herpesvirus-induced d T kinases resemble chick, monkey and human mitochondrial d T kinases in phosphate donor specificity, electrophoretic mobility and isoelectric point. Therefore, they could easily be confused with mitochondrial d T kinases, particularly when the herpesvirus d T kinases are present at very low concentrations

Disc PAGE, isoelectric focusing, and glycerol gradient centrifugation experiments were carried out to characterize thymidine (dT) kinase isozymes induced by herpesvirus of turkeys and infectious laryngotracheitis virus in the cytosol fraction of infected chick cells. The avian herpesvirus dT kinases differed from chick cytosol dT kinase in electrophoretic mobility, isoelectric point and phosphate donor specificity. The avian herpesvirus dT kinases resembled chick mitochondrial dT kinase in electrophoretic mobilityy and isoelectric point, but exhibited larger sedimentation coefficients. The avian herpesvirus enzymes closely resembled dT kinases induced by human herpes simplex viruses types 1 and 2.

To characterize and compare the thymidine (TdR) and deoxycytidine (CdR) kinase isozymes of uninfected and herpesvirus-infected cells: (i) the subcellular distribution of the isozymes has been studied; (ii) a specific assay for CdR kinase has been devised; (iii) the TdR kinase isozymes have been partially purified; and (iv) the purified enzymes have been analyzed by disc polyacrylamide gel electrophoresis, isoelectric focusing, and glycerol gradient centrifugation and by substrate competition and dCTP inhibition studies. The results indicate that there are interesting individual differences with respect to nucleoside acceptor specificity between the cytosol and mitochondrial pyrimidine deoxyribonucleoside kinases of uninfected cells and between the enzymes induced by different herpesviruses. In the cytosol of uninfected mouse, chicken, and owl monkey kidney cells, two different proteins, TdR kinase F and CdR kinase 2, catalyze the phosphorylations of TdR and CdR, respectively. TdR kinase F does not phosphorylate CdR, nor does CdR kinase 2 phosphorylate TdR. A second TdR kinase isozyme present in HeLa(BU25) mitochondria (TdR kinase B) also lacks CdR phosphorylating activity. In contrast, a genetically distinctive deoxypyrimidine kinase (TdR kinase A) of mouse, human, and chick mitochondria catalyzes the phosphorylation of both TdR and CdT. Three herpesviruses, marmoset herpesvirus and herpes simplex virus types 1 and 2, induce in the cytosol fraction of LM(TK-) mouse cells isozymes which share common properties with mitochondrial TdR kinase A, including the ability to catalyze the phosphorylation of both TdR and CdR. However, the herpesvirus-induced deoxypyrimidine kinases differ from mitochondrial TdR kinase A with respect to sedimentation coefficient, sensitivity to dCTP inhibition, and antigenic determinants. The herpesvirus-specific and the mitochondrial deoxypyrimidine kinases exhibit a preference for TdR over CdR as nucleoside acceptor. Pseudorabies virus and herpesvirus of turkeys induce cytosol TdR kinases resembling the other herpesvirus-induced TdR kinases in several properties, but like cellular TdR kinase F, the pseudorabies virus and herpesvirus of turkeys TdR kinases lack detectable CdR phosphorylating activities. Finally, a marmoset herpesvirus nutant resistant to bromodeoxyuridine, equine herpesvirus type 1, and Herpesvirus aotus induces neither TdR nor CdR phosphorylating enzymes during productive infections.