The papillomavirus life cycle begins with cells actively multiplying in epithelial cells of basal and parabasal layers. The differentiation of these cells is necessary for this virus to complete its life cycle. Transforming proteins E6 and E7 induce the S-phase in the lower epithelial layers.
When cells divide actively in basal and parabasal layers of epithelial cells, it initiates the papillomavirus lifecycle. This process is essential for the virus's progression. Proteins E6 and E7 trigger the S-phase in lower epithelial layers during this division.