A novel 50-kilodalton fragment of host cell factor 1 (C1) in G(0) cells.

Host cell factor 1 (HCF-1; also called C1) is a 230-kDa protein which is cleaved posttranslationally into separate but associated N- and C-terminal polypeptides. These polypeptides are components of the C1 complex, along with Oct-1 and the viral protein VP16. The C1 complex is formed when herpes simplex virus (HSV) infects a cell and is responsible for transcription of the HSV immediate-early genes. A temperature-sensitive mutation in the N-terminal kelch domain of HCF-1 reversibly arrests cells in a G(0)-like state when grown at the nonpermissive temperature, and the same domain interacts with VP16 in the formation of the C1 complex. The form of HCF-1 in primary G(0) cells was investigated by using peripheral blood mononucleocytes and serum-arrested human primary fibroblasts. A novel 50-kDa N-terminal fragment of HCF-1 encompassing the kelch domain was identified in the cytoplasm of these cells. This fragment arises by proteolysis of the full-length HCF-1 protein and is able to associate with VP16.

Improved synthesis and aminoacylation of p-nitrobenzophenone oxime polystyrene resin for solid-phase synthesis of protected peptides.

Procedures for the synthesis and acylation of p-nitrobenzophenone oxime polystyrene resin for the preparation of protected peptide segments have been reexamined. Friedel-Crafts acylation with p-nitrobenzoyl chloride is complete in less than one hour at room temperature. Conversion of the ketoresin to the corresponding oxime requires less than six hours at 85 degrees C. Carbodiimide-mediated coupling of tert-butyloxycarbonyl-amino acids to the oxime resin requires less than one hour. By varying the quantity of p-nitrobenzoyl chloride and aluminum chloride used for acylation, the oxime substitution level of the resulting resin can be controlled between 0.2 and 0.8 milliequivalents per gram of resin. Aminoacyl oxime resin can thus be prepared in one day.