THOC5 controls 3´end-processing of immediate early genes via interaction with CPSF100

Transcription of immediate early genes (IEGs) in response to extrinsic and intrinsic signals is tightly regulated at multiple stages. THOC5, a member of the TREX (transcription/export) complex plays a role in expression of only a subset of constitutively active genes. In this report, we show that THOC5 plays a role in the 3´end-processing of more than 90% of IEGs induced by serum stimulation, however THOC5 depletion does not influence the expression of the most rapidly induced IEGs, such as Fos or Jun. One group of THOC5 target genes, including Id1, Id3 and Wnt11 transcripts were not released from chromatin in THOC5 depleted cells. Another group of genes, such as Myc, and Smad7 transcripts, were released with shortening of 3´UTR by alternative cleavage, and were spliced but were exported to a lesser extent in THOC5 depleted cells. Furthermore, upon stimulation with serum THOC5 forms a complex with polyadenylation specific factor 100 (CPSF100). THOC5 is required for recruitment of CPSF100 to 3´UTR of THOC5 target genes, but not for THOC5 independent genes. These data suggest the presence of a novel mechanism for the control of immediate early genes response via 3´end-processing. In 2 dual-color microarray hybridizations, mRNA expression changes after 1h of FCS treatment were examined. MEF(Rosa26ERT2 Cre: THOC5 (flox/flox)) cells in which a THOC5 knockdown is inducible upon Tamoxifen treatment were analyzed. M4040 represents cells without Taxoxifen pre-treatment (wildtype reference) whereas M4041 represents the same celltype pre-treated for 2 days with Tamoxifen to induce a THOC5 knockdown.