title: Characterization of v-sis protein expressed in silkworm larvae using the Bombyx mori nuclear polyhedrosis virus vector.
abstract: The v-sis oncogene of simian sarcoma virus encodes a protein which is homologous to the human platelet-derived growth factor B-chain. The v-sis protein undergoes a series of processing steps including dimer formation and proteolytic digestion to generate several molecular sizes of the protein. Two of these v-sis proteins were expressed alone or as polyhedrin-sis fusion proteins using the Bombyx mori nuclear polyhedrosis virus vector. The polyhedrin-sis fusion proteins contained a collagenase-sensitive site at the junction. The expression levels of the fusion proteins whose polyhedrin portions consisted of only 8 amino-terminal amino acids were 3-4 times higher than those of non-fusion proteins. One of these fusion proteins was expressed in silkworm larvae and the v-sis protein was isolated from the fusion protein by collagenolysis followed by chromatography. Because the purified v-sis protein exhibited the same molecular size on SDS-polyacrylamide gels under reducing and non-reducing conditions, it was concluded to be monomeric in structure. It possessed chemotactic activity but lacked mitogenic activity. In addition, a small amount (approximately 1%) of monomeric v-sis protein was converted in vitro to the mitogenically active v-sis protein, which could be a homo-dimer.
authors.affiliation: Research Institute, Daiichi Pharmaceutical Co., Ltd., Tokyo.
authors.forename: K
authors.initials: K
authors.lastname: Morishita
authors.forename: K
authors.initials: K
authors.lastname: Sakano
authors.forename: K
authors.initials: K
authors.lastname: Takeda
authors.forename: S
authors.initials: S
authors.lastname: Maeda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D004279:DNA, Viral / Q000235:genetics; D005822:Genetic Vectors; D008969:Molecular Sequence Data; D020575:Oncogene Proteins v-sis; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D015682:Retroviridae Proteins, Oncogenic / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D004279:DNA, Viral; D020575:Oncogene Proteins v-sis; D011993:Recombinant Fusion Proteins; D015682:Retroviridae Proteins, Oncogenic