Biomedical subjects

B R Franza

Publications and source records attributed to B R Franza.

58 records · Page 4Linked to original sources

PubMed1975

Activation of human prothrombin by a procoagulant fraction from the venom of Echis carinatus. Identification of a high molecular weight intermediate with thrombin activity.

In the presence of a procoagulant fraction (Echis carinatus procoagulant) isolated from the venom of the saw-scaled viper Echis carinatus sochureki, purified human prothrombin (P1) is completely converted to thrombin. The first step is the removal of an NH2-terminal peptide (F1) representing approximately one-third of the prothrombin molecule. The remaining peptide (P2) is then cleaved by the action of E.c. procoagulant to yield a two-chain, disulfide-bridged protein (P'2) which has the same molecular weight as P2. P'2 has enzymic (thrombin) activity, as evidence by incorporation of radiolabeled diisopropylphosphate into its heavy chain (TB), hydrolysis of p-toluenesulfonylarginine methyl ester, and clotting of fibrinogen. Relative to thrombin, its esterolytic activity greatly exceeds its clot-promoting activity. Examination of the polypeptide chains obtained by reducing P'2 has shown that its larger chain (TB) is indistinguishable from the heavy chain of thrombin. Its other chain (F2TA) consists of the light chain (TA) of thrombin bound by peptide linkage to the protion of the prothrombin molecule which had been adjacent to F1. Removal of this portion (F2) is catalyzed by thrombin (and, evidently, by P'2), but not by the E.c. procoagulant. When F2 is removed from P'2, the remaining two-chian protein is indistinguishable from thrombin by any of the criteria applied--molecular weight, subunit chain composition, or enzymic activity. Polyacrylamide gel electrophoresis was carried out in sodium dodecyl sulfate before and after disulfide reduction of samples generated in the presence and in the absence of diisopropylphosphorofluoridate, which inhibits thrombin but not the E.c. procoagulant. Such experiments showed that thrombin (and probably P'2), as well as E.c. procoagulant, catalyzes the release of F1. Furthermore, thrombin brings about the cleavage of F1 to yield a two-chain, disulfidebridged protein (F'1). These observations, particularly those made in the course of characterizine P'2, have led to the conclusion that cleavage of the peptide bond connecting the TA and TB portions of the prothrombin molecule (or its derivatives) produces a serine active center and, hence, a molecule possessing thrombin activity. This cleavage is catalyzed by the E.c. procoagulant but not by thrombon itself.

Animals↗

PubMedDate not supplied

Identity of the proliferating cell nuclear antigen and cyclin.

Studies of growth regulation and cellular transformation will be assisted by the identification of proteins that are preferentially synthesized in dividing cells. The 'proliferating cell nuclear antigen' ( PCNA ), distinguished by its apparent association with cell division, is defined by reaction with an antibody found in the autoimmune disease systemic lupus erythematosus (SLE). This antibody reacts with proliferating cells including tumour cells but gives weak or undetectable immunofluorescence with resting cells of normal tissues. Peripheral blood lymphocytes are devoid of PCNA until activated by mitogen in vitro. In synchronized cultures its level and distribution fluctuate through the cell cycle, with a striking accumulation in the nucleolus late in the G1 phase and early in the S phase. Many of these properties are shared by ' cyclin '. This nuclear protein, identified by its position in a two-dimensional separation of cell proteins, is also transformation-sensitive and is preferentially synthesized in the S phase. We establish here that PCNA and cyclin are identical, and show that PCNA is an acidic nuclear protein of apparent molecular weight 35,000.

Animals↗

PubMedDate not supplied

Characterization of cellular proteins recognizing the HIV enhancer using a microscale DNA-affinity precipitation assay.

Numerous nucleic acid sequence motifs have been identified as transcriptional regulatory elements, and proteins involved in the control of gene replication and transcription have been successfully purified using nucleic acid affinity procedures. We have developed an assay that allows direct characterization of cellular proteins binding to the enhancer element of the human immunodeficiency virus (HIV), which is analogous to immunoprecipitation techniques. In extracts of H9 cells, a human CD4+ lymphoblast line clonally selected for its ability to support HIV replication, we find a class of proteins that interact specifically with the HIV enhancer. Reproducible high-resolution, two-dimensional gel electrophoresis has allowed us to resolve these proteins into two major sets. One set is common to H9 cells, two human B-lymphoblast lines, and a phytohaemagglutinin (PHA)-stimulated human CD4+ lymphoblast line (Jurkat). A second set of proteins is found only in H9 cells. Thus, with this assay we have identified HIV enhancer-binding proteins that are constitutive or inducible and that are cell-type specific.

Base Sequence↗

PubMedDate not supplied

BCR/ABL modulates the cytokine and retinoic acid response of c-Rel in human myeloid cells.

A human myeloid cell line, Mo7, and a daughter cell line expressing the bcr/abl oncogene, Mo7-P210, were used in a comparative study analyzing the effects of p210BCR/ABL expression on tyrosine phosphorylation, specific DNA binding and expression of the proto-oncoprotein c-Rel. The steady state expression of c-Rel was indistinguishable in both cell lines. Tyrosine phosphorylation and DNA binding of c-Rel were slightly elevated in Mo7-P210 cells. Further, Mo7 and Mo7-P210 cells showed different responses concerning c-Rel after stimulation with cytokines and retinoic acid. The results presented here demonstrate that c-Rel can be modulated by hematopoietic cytokines and suggest that bcr/abl expression has an impact on these responses and that c-Rel may be a downstream effector for p210BCR/ABL.

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