<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Networks of gene expression control in Trypanosoma brucei"^^ . "Since in trypanosomes most protein-coding genes are constitutively transcribed by RNA polymerase II in a polycistronic manner, gene expression is mainly regulated at the post-transcriptional level. It is therefore interesting to investigate the relevant regulatory factors. In a previous genome-wide tethering screen hundreds of putative mRNA-fate regulators were found, including the proteins BFR1L, an up-regulator of gene expression, and ZC3H5, a down-regulator of gene expression.\r\nBFR1L has some similarities to yeast Bfr1p, an ER- and polysome-associated protein. BFR1L displays in vivo mRNA binding although it lacks canonical RNA-binding domains. Double-knockout bloodstream form trypanosomes displayed a slight growth defect. By immunofluorescence microscopy, a tagged version was located in the cytoplasm and overlapped partially with an ER marker. RNA pull-down analysis suggested that most of the BFR1L-bound mRNAs encode ribosomal proteins, but no common RNA motif could be found by in silico analysis. The mRNAs encoding ribosomal proteins are known not to sequester in granules upon starvation stress or heat shock. Similarly, BFR1L protein did not go to granules under starvation stress. It is tempting to speculate that the interaction remains active during stress, and targeting of the mRNAs to the ER could prevent sequestration into granules and could keep the mRNAs in ribosomes. The attachment of BFR1L to the ER could be mediated via the putative interaction partner Tb927.9.9550, which has a transmembrane domain.\r\nZC3H5 knock-down led to a fast growth defect, killing the cells after 48 h of RNAi induction. We therefore analyzed the RNAi effect on growth kinetics, protein levels, nuclei/kinetoplasts ratios and the transcriptome at different time points. After RNAi induction, the proportion of 2N2K cells increased rapidly. In addition, the ZC3H5 RNAi cells often possessed abnormal and higher numbers of nuclei and kinetoplast. While short-term down-regulation of ZC3H5 showed only a minor effect with respect to the transcriptome, an increase of mRNAs encoding ribosomal proteins, the increase of the monosomal peak without an increase of mRNAs in this fraction, the occurrence of half-mers as well as an increase of mRNAs encoding ribosomal proteins in the free fraction were observed with respect to the polysomal profiles. This suggest that the ribosome assembly is disturbed upon knock-down of ZC3H5. However, this seems to be a secondary effect. RNA pull-down analysis suggested that ZC3H5 binds mRNAs encode cytoskeleton proteins. Tandem Affinity Purification of ZC3H5 followed by MS analysis revealed three putative interaction partners which were validated by co-immunoprecipitation (Tb927.8.1500, Tb927.7.3040 and Tb927.11.4900). In addition, tethering of ZC3H5 and its interaction partners to a CAT reporter showed that the proteins are repressors; thus, we have identified a novel repressor complex that may regulate genes required for cell cycle progression. The exact mechanism of action is not known at the moment, but it is tempting to speculate that the function of Tb927.11.4900 as a G protein is responsible for the association and dissociation of the complex. This could be cell cycle dependent, because the target mRNAs peak in S-phase. Maybe the ZC3H5 complex represses its targets during the rest of the cell cycle and targets are de-repressed in S-phase to produce the proteins needed for cytokinesis."^^ . "2019" . . . . . . . "Kathrin"^^ . "Bajak"^^ . "Kathrin Bajak"^^ . . . . . . "Networks of gene expression control in Trypanosoma brucei (PDF)"^^ . . . "Bajak, Kathrin_Dissertation.pdf"^^ . . . "Networks of gene expression control in Trypanosoma brucei (Other)"^^ . . . . . . "indexcodes.txt"^^ . . "HTML Summary of #26942 \n\nNetworks of gene expression control in Trypanosoma brucei\n\n" . "text/html" . . . "500 Naturwissenschaften und Mathematik"@de . "500 Natural sciences and mathematics"@en . . . "570 Biowissenschaften, Biologie"@de . "570 Life sciences"@en . .