Cloning and characterization of E2F-2, a novel protein with the biochemical properties of transcription factor E2F.

E2F is a mammalian transcription factor that appears to play an important role in cell cycle regulation. While at least two proteins (E2F-1 and DP-1) with E2F-like activity have been cloned, studies from several laboratories suggest that additional homologs may exist. A novel protein with E2F-like properties, designated E2F-2, was cloned by screening a HeLa cDNA library with a DNA probe derived from the DNA binding domain of E2F-1 (K.

Transcription factor E2F binds DNA as a heterodimer.

E2F is a mammalian transcription factor that appears to play an important role in cell cycle control. DNA affinity column-purified E2F from HeLa cells reproducibly exhibits multiple protein bands when analyzed by SDS/PAGE. After electrophoretic purification, electroelution, and refolding of the individual protein components, the E2F DNA binding activity of the individual proteins was poor.

Papillomavirus E7 protein binding to the retinoblastoma protein is not required for viral induction of warts.

Human papillomaviruses (HPVs) are the etiologic agents responsible for benign epithelial proliferative disorders including genital warts and are a contributory factor in the pathogenesis of cervical cancer. HPVs demonstrate strict species and cell-type specificity, which is manifested by the inability of these viruses to induce disease in any species other than humans. The natural history of HPV infection in humans is closely mimicked by cottontail rabbit papillomavirus (CRPV) infection in domestic laboratory rabbits.

Comparison of the binding of the human papillomavirus type 16 and cottontail rabbit papillomavirus E7 proteins to the retinoblastoma gene product.

Binding of the human papillomavirus type 16 (HPV-16) E7 oncoprotein to the retinoblastoma protein (pRb) is thought to be involved in the cellular transformation mediated by HPV-16. Here we show that the E7 protein of the cottontail rabbit papillomavirus (CRPV) binds to the same C-terminal portion of human pRb as HPV-16 E7, and that both the CRPV and HPV-16 E7 proteins bind specifically through similar domains to rabbit pRb. Furthermore, a single amino acid substitution which reduces the binding of HPV-16 E7 to human pRb also abolishes binding of CRPV E7 to both human and rabbit pRb.

Mutational analysis of an inherently defective translation initiation site.

In a reverse of many studies of translational initiation sites, we have explored the basis for the inactivity of an apparently defective initiation site. Gene VII of the filamentous phage f1 has a translational start site with highly unusual functional properties and a sequence dissimilar to a prokaryotic ribosome binding site. The VII site shows no activity in assays of independent initiation, even in a deletion series designed to remove potentially interfering RNA secondary structure.