Regulation of human papillomavirus late gene expression.

Human papillomaviruses (HPVs) comprise a large group of small DNA tumor viruses with tropism for squamous epithelial cells. The papillomavirus life cycle is strictly linked to the epithelial differentiation program and production of virus particles is dependent on terminal cell differentiation. The virus structural proteins L1 and L2 are therefore detected only in the upper layers with differentiated cells in the infected epithelium. This property is common to all known HPVs. However, the abundance of virus particles detected in vivo may vary between the various HPV types and one can divide the HPV types according to the amount of virus they produce. It is reasonable to speculate that the differentiation dependent production of L1 and L2 and the differences in L1 and L2 protein levels among various HPV types reflect an adaptation of the viruses to the environment of the host that results in escape from the immune surveillance for various periods of time and efficient transmission of virus in the human population. Our research group is interested in the regulation of expression of the HPV structural proteins L1 and L2. The results of our research are summarised in this article.