Transforming Sloan-Kettering viruses generated from the cloned v-ski oncogene by in vitro and in vivo recombinations

Abstract

The Sloan-Kettering viruses (SKVs) are replication-defective retroviruses that transform avian cells in vitro. Each of the three SKV isolates is a mixture of viruses with genomes ranging in size from 4.1 to 8.9 kilobases (kb) with a predominant genome of 5.7 kb. Using a cDNA representing a sequence, v-ski, that is SKV specific and held in common by the multiple SKV genomes, we generated a restriction map of the 5.7-kb SKV genome and molecularly cloned a ski-containing fragment from SKV proviral DNA. Southern hybridization and sequence analysis showed that the cloned DNA fragment consisted of the 1.3-kb ski sequence embedded in the p199a9 sequence and followed by the remaining 5' half of the gag gene and small portions of both the pol and env genes. A large deletion encompassing the 3' half of gag and the 5' 80% of pol was mapped to a position about 1 kb downstream from the 3' ski-gag junction. To determine whether the cloned ski sequence had transforming activity, the ski-containing fragment and a cloned Rous-associated virus 1 (RAV-1) genome were used to construct an analog of the 5.7-kb SKV genome, RAV-SKV. Cotransfection of chicken embryo cells with RAV-SKV and RAV-1 yielded foci of transformed cells whose morphology was identical to that induced by the natural SKVs. The transformed transfected cells produced transforming virus with a 5.7-kb ski-containing genome and synthesized a gag-containing polyprotein of 110 kilodaltons (kDa). Several nonproducer clones of RAV-SKV-transformed cells were analyzed, and most were found to synthesize a 5.7-kb SKV RNA and a 110-kDa polyprotein. One clone was found to contain an 8.9-kb SKV RNA, and this clone synthesized a 125-kDa polyprotein. Since both the 5.7-and 8.9-kb genomes and the 110-and 125-kDa polyproteins had been identified in studies on the natural SKVs, the present results not only demonstrate the transforming activity of these individual SKVs but also suggest mechanisms for their generation.

Trans-regulation of myogenin promoter/enhancer activity by c-ski during skeletal-muscle differentiation: the C-terminus of the c-Ski protein is essential for transcriptional regulatory activity in myotubes

“…The ski oncogene (v-ski), which was originally isolated from Sloan-Kettering avian retroviruses, has been shown to cause anchorage-independent growth and morphological transformation and to induce myogenesis in itro [1][2][3][4]. c-ski, the cellular counterpart of v-ski, is also capable of inducing not only expression of MyoD and myogenin in otherwise non-myogenic quail embryo cells but also morphological transformation of chicken embryo cells when overexpressed [5].…”

Common mechanism of retrovirus activation and transduction of c-mil and c-Rmil in chicken neuroretina cells infected with Rous-associated virus type 1

“…They were initially identified through their association with retroviruses, acting as natural transducing vectors (38). Generation of replication-defective retroviruses carrying transforming genes proceeds through multiple recombination events and results in alteration of both viral and cellular sequences (3,28,32,37,40). These successive steps during in vivo transduction are difficult to dissect.…”

Ski drives an acute increase in MMP-9 gene expression and release in primary cardiac myofibroblasts

“…Importantly, some evidence exists to indicate that Ski is a scaffolding protein that may bind to transcription factors such as c-Jun (Pessah et al 2002). Previous studies confirm that Ski binds to a variety of transcription factors and can act as both a co-activator and co-repressor, depending on its binding partners (Stavnezer et al 1986;Nicol and Stavnezer 1998;Nomura et al 1999) which may lend the fibroblast a modicum of flexibility with respect to a response to a given stimulus. Additionally, abnormal Ski compartmentalization as observed in MFB of the infarct scar of post-MI hearts (Cunnington et al, 2011) may underpin the adverse remodeling and facilitate chronic cardiac fibrosis in the diseased myocardium (Fig.…”