wild-type cells, indicating they are only partially degraded by the exosome and are able to escape the Nrd1-Nab3-Sen1 pathway. SUTs are primarily degraded instead by the combined activity of the decapping enzymes Dcp1, Dcp2 and the cytoplasmic exonuclease Xrn1. One class of SUTs has been found to participate in the trans-silencing of a retrotransposon. Interaction with histones CUT repression Within yeast models, it has been observed that the histone methyltransferase Set2 is critical for maintaining proper methylation at histone 3 lysine 36 (H3K36). Loss of Set2 function results in loss of H3K36 methylation and over-acetylation on histone H4, allowing for the expression of several short cryptic transcripts from the genes STE11 and FLO8. In this case, the loss of Set2 allows for the expression of exon-derived CUTs as opposed to intergenic-derived transcripts, showing the role that histones play in controlling intragenic-derived CUTs. In the absence of the transcription elongation factors Spt6 and Spt16, nucleosomes distribute incorrectly across DNA, allowing for RNA polymerase II to access cryptic polymerase sites and erroneously transcribe CUTs. Spt6 is responsible for restoring normal chromatin structure following transcription from RNA polymerase II, and yeast cells with compromised Spt6 function have been found to produce an increased number of CUTs. For instance, RNA polymerase II has been observed to bind incorrectly to the interior initiation region of the FLO8 gene in spt6 mutants, allowing for cryptic transcription to occur due to an erroneous nucleosome distribution. Histone eviction/recruitment through CUTs A cryptic transcript located at the promoter of PHO5 that is detectable in Δrrp6 mutants is responsible for increasing the speed of promoter remodeling. Knock-out mutants without the ability to transcribe the CUT have about half the rate of histone eviction from the PHO5 promoter compared to wild-type cells, implying that the CUT is responsible for mediating the accessibility of the PHO5 promoter to RNA Polymerase II. It has also been observed in S. cerevisiae that Δrrp6 and Δtrf4 mutants have repressed transcription of the gene PHO84. Δrrp6 and Δtrf4 cells have stabilized levels of PHO84 antisense transcripts, which serve to recruit the Hda1/2/3 histone deacetylase complex to the PHO84 gene, effectively silencing transcription and expression through histone deacetylation. In Δrrp6 cells, Hda1 associates with the promoter or coding regions of PHO84 up to five times more often than in wild-type counterparts. Additionally, histone deacetylation activity occurs specifically at the region of PHO84 and Hda1 overlap on histone