The high-risk HPV E6 oncoprotein preferentially targets phosphorylated nuclear forms of hDlg.
High-risk mucosal HPV E6 oncoproteins target a number of PDZ domain-containing substrates for proteasome mediated degradation. One of these, Discs Large (Dlg), is involved in the regulation of cell polarity and proliferation control. Previous studies had suggested that Dlg when hyperphosphorylated by osmotic shock, or when present in the nucleus could be preferentially targeted by E6. In this study we use phospho-specific antibodies directed against Dlg phosphorylated at residues S158 and S442 to show that these two observations are, in fact, linked. Dlg, when phosphorylated on S158 and S442 by CDK1 or CDK2, shows a preferential nuclear accumulation. However, these forms of Dlg are absent in cells derived from HPV-induced cervical cancers. Upon either proteasome inhibition or siRNA ablation of E6 expression, we see specific rescue of these phosphorylated forms of Dlg. These results demonstrate that nuclear forms of Dlg phosphorylated on its CDK phospho-acceptor sites has enhanced susceptibility to E6-induced degradation and place previous studies on the stress-induced phosphorylation of Dlg into a relevant biological context.
Narayan
Nisha
N
Tumour Virology Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano 99, Trieste, TS 34012, Italy.
Subbaiah
Vanitha Krishna
VK
Banks
Lawrence
L
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D018929:Cell Culture Techniques; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism* / Q000821:virology; D002467:Cell Nucleus / Q000378:metabolism; D000074288:Discs Large Homolog 1 Protein; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006367:HeLa Cells; D052162:Human papillomavirus 16 / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D012694:Serine / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; D000074288:Discs Large Homolog 1 Protein; C068651:E6 protein, Human papillomavirus type 16; D008565:Membrane Proteins; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D012694:Serine; D046988:Proteasome Endopeptidase Complex