Telomere length regulation and transcriptional silencing in KU80-deficient Trypanosoma brucei. 2004

Christian J Janzen, and Fabian Lander, and Oliver Dreesen, and George A M Cross
Laboratory of Molecular Parasitology, The Rockefeller University, Box 185, 1230 York Avenue, New York, NY 10021-6399, USA.

KU is a heterodimer, consisting of approximately 70 and approximately 80 kDa subunits (KU70 and KU80, respectively), which is involved in a variety of nuclear functions. We generated tbKU80-deficient trypanosomes to explore the potential role of the tbKU complex in telomere maintenance and transcriptional regulation of variant surface glycoprotein (VSG) genes in Trypanosoma brucei. Using real-time PCR, we demonstrated that the expression of several different VSG genes remains tightly regulated in tbKU80-deficient bloodstream-form cell lines, suggesting that VSG transcription profiles do not change in these cells. Owing to developmental silencing of the VSG Expression Sites (ES), no VSG is transcribed in the insect procyclic stage. With a green fluorescent protein reporter system, we showed that tbKU80-deficient mutants are fully capable of ES silencing after differentiation into procyclic forms. Using T7 RNA polymerase to explore the transcriptional accessibility of ES chromatin in vivo, we demonstrated that tbKU80-deficient bloodstream-form cells were able to generate transcriptionally repressed ES chromatin after differentiation into procyclic cells. Finally, we demonstrated progressive telomere shortening in tbKU80-deficient mutants. The possible function of tbKU80 in telomere maintenance and regulation of telomerase is discussed.

UI MeSH Term Description Entries
D002460 Cell Line Established cell cultures that have the potential to propagate indefinitely. Cell Lines,Line, Cell,Lines, Cell
D002843 Chromatin The material of CHROMOSOMES. It is a complex of DNA; HISTONES; and nonhistone proteins (CHROMOSOMAL PROTEINS, NON-HISTONE) found within the nucleus of a cell. Chromatins
D004268 DNA-Binding Proteins Proteins which bind to DNA. The family includes proteins which bind to both double- and single-stranded DNA and also includes specific DNA binding proteins in serum which can be used as markers for malignant diseases. DNA Helix Destabilizing Proteins,DNA-Binding Protein,Single-Stranded DNA Binding Proteins,DNA Binding Protein,DNA Single-Stranded Binding Protein,SS DNA BP,Single-Stranded DNA-Binding Protein,Binding Protein, DNA,DNA Binding Proteins,DNA Single Stranded Binding Protein,DNA-Binding Protein, Single-Stranded,Protein, DNA-Binding,Single Stranded DNA Binding Protein,Single Stranded DNA Binding Proteins
D000072200 Ku Autoantigen An ATP-dependent DNA HELICASE that preferentially binds SINGLE-STRANDED DNA. It is a heterodimer consisting of an 80 kDa subunit (XRCC5) and 70 kDa subunit (XRCC6) that functions with DNA LIGASE IV in the repair of DOUBLE-STRANDED DNA BREAKS and V(D)J RECOMBINATION. G22P1 Antigen,Ku Antigen,Ku Autoantigen, 70 kDa,Ku Autoantigen, 80 kDa,Ku Heterodimer,Ku Protein,Ku70 Antigen,Ku80 Antigen,X-ray Repair Cross-Complementing Protein 5,X-ray Repair Cross-Complementing Protein 6,XRCC5 Protein,XRCC6 Protein,Antigen, G22P1,Antigen, Ku,Antigen, Ku70,Antigen, Ku80,Autoantigen, Ku,Heterodimer, Ku,X ray Repair Cross Complementing Protein 5,X ray Repair Cross Complementing Protein 6
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D014158 Transcription, Genetic The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION. Genetic Transcription
D014346 Trypanosoma brucei brucei A hemoflagellate subspecies of parasitic protozoa that causes nagana in domestic and game animals in Africa. It apparently does not infect humans. It is transmitted by bites of tsetse flies (Glossina). Trypanosoma brucei,Trypanosoma brucei bruceus,Trypanosoma bruceus,brucei brucei, Trypanosoma,brucei, Trypanosoma brucei,bruceus, Trypanosoma,bruceus, Trypanosoma brucei
D014643 Variant Surface Glycoproteins, Trypanosoma Glycoproteins attached to the surface coat of the trypanosome. Many of these glycoproteins show amino acid sequence diversity expressed as antigenic variations. This continuous development of antigenically distinct variants in the course of infection ensures that some trypanosomes always survive the development of immune response to propagate the infection. Surface Variant Glycoproteins, Trypanosoma,Trypanosoma Variant Surface Coat Glycoproteins,SSP-4,VSG 117,VSG 118,VSG 221
D016615 Telomere A terminal section of a chromosome which has a specialized structure and which is involved in chromosomal replication and stability. Its length is believed to be a few hundred base pairs. Telomeres
D017353 Gene Deletion A genetic rearrangement through loss of segments of DNA or RNA, bringing sequences which are normally separated into close proximity. This deletion may be detected using cytogenetic techniques and can also be inferred from the phenotype, indicating a deletion at one specific locus. Deletion, Gene,Deletions, Gene,Gene Deletions

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