In previous studies, we have observed that significantly disrupting the cell cycle and extended doubling times can nonspecifically increase BMV RNA levels per cell, apparently because the virus has more time to accumulate RNA replication products prior to cell division (unpublished data). To avoid such false positives, we excluded from further analysis strains for which doxtreatment significantly slowed cell division (see Results above). Thus, although SPC29 and PFY1 encode proteins potentially related to cell division (respectively a spindle pole body protein and actin-binding protein) the doubling times of untreated and doxtreated P TET -SPC29 and P TET -PFY1 cells were comparable and likely do not account for the increased levels of BMV RNA4 observed (Fig. 2. and Table 3 ). Alternatively, disrupting the cell cycle in P TET -SPC29-and/or P TET -PFY1-repressed cells may alter cell cycle signal transduction pathways or the localization of cellular factors that normally inhibit viral RNA replication.