Genetic Analysis of the Human Papillomavirus Type 31 Differentiation-Dependent Late Promoter

Abstract

Human papillomaviruses infect stratifying squamous epithelia, causing benign and malignant lesions. Upon differentiation of the host keratinocyte, the virus undergoes a dramatic increase in both DNA replication and transcription from the late promoter, leading to expression of late genes and virion morphogenesis. In human papillomavirus type 31 (HPV31), the late promoter is designated p742 and includes multiple start sites embedded within the E7 gene. In this report, we mapped viral DNA elements that control transcriptional activity from p742. Enhancer elements in the viral upstream regulatory region positively regulate this promoter. The region containing the transcriptional start sites is dispensable for activity, and at least two separate elements in the E6/E7 region are capable of supporting transcription. Of these, we mapped one to a 150-bp region of the E7 open reading frame and designate it the core p742 promoter. Using GF109203X, an inhibitor of protein kinase C signaling, we show that p742 activation is independent of viral genome amplification. Finally, we mapped elements in the region of p742 that confer responsiveness to differentiation and show that the upstream regulatory region does not contribute to the differentiation response of p742. These studies are an important step toward understanding the functioning and regulation of this multiple-start promoter.

The E7 Open Reading Frame Acts in cis and in trans To Mediate Differentiation-Dependent Activities in the Human Papillomavirus Type 16 Life Cycle

“…As expected, promoter activity was detected using the wild-type sequences, as shown by increased luciferase production relative to that of the empty vector. The activity of the wild-type reporter increased by approximately 2.5-fold in MC culture and is consistent with previous reports (5,46). In contrast, each of the mutant reporters showed a defect in basal reporter activity as well as in the fold difference in activity between differentiated and undifferentiated conditions.…”

p63 Is Necessary for the Activation of Human Papillomavirus Late Viral Functions upon Epithelial Differentiation

“…In lentivirus-transduced, HPV-positive cells in which p63 expression levels were reduced by shRNAs, differentiation-dependent late transcripts, as well as genome amplification, were reduced. Previous studies have shown that activation of the differentiation-dependent late promoter is not necessarily dependent upon genome amplification and can occur at low levels in its absence (1,40). This indicates that the retention of p63 is needed for the activation of HPV late viral functions.…”

Characterization of Transcription Factor Binding to Human Papillomavirus Type 16 DNA during Cellular Differentiation

“…Similarly, a deletion analysis of the late promoter of HPV-31 has revealed many regions and protein factors that are also important in the activation of the late promoter during differentiation (34). It has also been shown that activation of the late HPV-31 promoter during differentiation is independent of viral genome amplification (4,34).…”