Required to activate transcription of PDR3, a gene involved in retrograde regulation of multidrug resistance, a phenomenon that takes place in cells that have lost their mitochondrial genome. Also required for ubiquitination of histone H2B to form H2BK123ub1. H2BK123ub1 gives a specific tag for epigenetic transcriptional activation, telomeric silencing, and is also a prerequisite for H3K4me and H3K79me formation. Its precise role in H2BK123ub1 formation however is unclear and is independent of retrograde regulation of multidrug resistance function. Probably interacts with BRE1. Present with 2060 molecules/cell in log phase SD medium.