Principal Component Analysis of the prediction of TFBS in the URR of the papillomaviruses. The predictions of the presence/absence of TFBS in the URR of the papillomaviruses were analysed by principal component analysis. The figure shows the distribution of alpha and beta papillomaviruses according to the two principal components, PC1 and PC2. Beta papillomaviruses, in grey, cluster together in the upper-right quadrant, whereas alpha papillomaviruses are distributed throughout the other three quadrants. Beta papillomaviruses are therefore more homogeneous according to the principal component analysis of TFBS in the URR than alpha papillomaviruses. This higher diversity in the alpha papillomaviruses is also observed regarding the higher number of species comprised in this genus and to the diversity in their clinical manifestations.