Identification of MicroRNAs That Stabilize p53 in Human Papillomavirus-Positive Cancer Cells.

Etiologically, 5% of all cancers worldwide are caused by the high-risk human papillomaviruses (hrHPVs). These viruses encode two oncoproteins (E6 and E7) whose expression is required for cancer initiation and maintenance. Among their cellular targets are the p53 and the retinoblastoma tumor suppressor proteins.

Live cell, image-based high-throughput screen to quantitate p53 stabilization and viability in human papillomavirus positive cancer cells.

Approximately 5% of cancers are caused by high-risk human papillomaviruses. Although very effective preventive vaccines will reduce this cancer burden significantly over the next several decades, they have no therapeutic effect for those already infected and remaining at risk for malignant progression of hrHPV lesions. HPV-associated cancers are dependent upon the expression of the viral E6 and E7 oncogenes.

Angelman syndrome-associated point mutations in the Zn-binding N-terminal (AZUL) domain of UBE3A ubiquitin ligase inhibit binding to the proteasome.

Deregulation of the HECT ubiquitin ligase UBE3A/E6AP has been implicated in Angelman syndrome as well as autism spectrum disorders. We and others have previously identified the 26S proteasome as one of the major UBE3A-interacting protein complexes. Here, we characterize the interaction of UBE3A and the proteasomal subunit PSMD4 (Rpn10/S5a).

Network Analysis of UBE3A/E6AP-Associated Proteins Provides Connections to Several Distinct Cellular Processes.

Perturbations in activity and dosage of the UBE3A ubiquitin-ligase have been linked to Angelman syndrome and autism spectrum disorders. UBE3A was initially identified as the cellular protein hijacked by the human papillomavirus E6 protein to mediate the ubiquitylation of p53, a function critical to the oncogenic potential of these viruses. Although a number of substrates have been identified, the normal cellular functions and pathways affected by UBE3A are largely unknown.

Proteomic analysis and identification of cellular interactors of the giant ubiquitin ligase HERC2.

HERC2 is a large E3 ubiquitin ligase with multiple structural domains that has been implicated in an array of cellular processes. Mutations in HERC2 are linked to developmental delays and impairment caused by nervous system dysfunction, such as Angelman Syndrome and autism-spectrum disorders. However, HERC2 cellular activity and regulation remain poorly understood.

Identification and proteomic analysis of distinct UBE3A/E6AP protein complexes.

The E6AP ubiquitin ligase catalyzes the high-risk human papillomaviruses' E6-mediated ubiquitylation of p53, contributing to the neoplastic progression of cells infected by these viruses. Defects in the activity and the dosage of E6AP are linked to Angelman syndrome and to autism spectrum disorders, respectively, highlighting the need for precise control of the enzyme. With the exception of HERC2, which modulates the ubiquitin ligase activity of E6AP, little is known about the regulation or function of E6AP normally.

Brd4 regulation of papillomavirus protein E2 stability.

The papillomavirus (PV) E2 protein is an important regulator of the viral life cycle. It has diverse roles in viral transcription, DNA replication, and genome maintenance. Our laboratory has previously identified the cellular bromodomain protein Brd4 as a key interacting partner of E2.