DIFFERENTIAL REGULATION OF HUMAN PAPILLOMAVIRUS TYPE-6 AND TYPE-11 EARLY PROMOTERS IN CULTURED-CELLS DERIVED FROM LARYNGEAL PAPILLOMAS

Cells cultured from laryngeal papillomas contain episomal human papill omavirus type 6 or type 11 (HPV-6/11) DNA, We developed a sensitive RN ase protection assay to simultaneously measure expression from the HPV E6, E7, and E1 promoters (P1, P2, and P3, respectively) in this manip ulable culture system and found that P1, P2, and P3 transcript abundan ces could be independently modulated by culture medium composition and culture substrate, In undifferentiated cells grown in a low-calcium s erum-free medium, P1 transcripts commonly predominated over those from P2, P3 transcripts were often undetectable, and high concentrations o f retinoic acid were able to selectively decrease P2 transcript abunda nce, When cultures were allowed to stratify and differentiate by growt h on a collagen gel at the air liquid interface, total HPV RNA increas ed up to sixfold because of selective increases in abundances of P1 an d P3 transcripts, High-calcium submerged cultures also showed easily d etectable P3 transcripts, and isolated suprabasal cells contained almo st exclusively these transcripts, Growth arrest alone was not sufficie nt to induce P3 transcripts, Thus, in contrast to the HPV-6/11 E6 and E7 promoters, the E1 promoter was utilized primarily in a differentiat ion-specific manner. We also show that increased HPV gene dosage will not necessarily bring about increased HPV transcript abundance, sugges ting that other viral and cellular factors are responsible far regulat ion of total transcript levels as well as specific promoter usage.