Why should cell biologists study microbial pathogens?

Welch, Matthew D.

Cell cycle regulatory mechanisms have also been exposed through the investigation of virus interactions with host cells (Bagga and Bouchard, 2014) . Classic examples involve the study of DNA tumor viruses, which include adenovirus, human papilloma virus, and SV40. These viruses rely on the host DNA replication machinery, and thus they induce cell cycle progression into S phase to favor viral DNA replication. A key discovery was that these viruses encode proteins, such as E1A from adenovirus, that bind to the tumor-suppressor protein pRb and related proteins (Whyte et al., 1988) . The role of pRb as a negative regulator of cell cycle progression was subsequently revealed when it was found that E1A binding to pRb competes with and releases the bound transcription factor E2F, which turn activates the expression of cell cycle regulatory genes that promote entry into S phase Bandara and La Thangue, 1991; Chellappan et al., 1991; Raychaudhuri et al., 1991) . Other viruses target different cell cycle regulators, including Cdks and cyclins (Bagga and Bouchard, 2014) , and studying how viruses manipulate host cells will continue to reveal cell cycle regulatory mechanisms.