telobox Dotaz Zobrazit nápovědu
Telobox is a Myb-related DNA-binding domain which is present in a number of yeast, plant and animal proteins. Its capacity to bind preferentially double-stranded telomeric DNA has been used in numerous studies to search for candidate telomeric proteins in various organisms, including plants. Here we provide an overview of these studies with a special emphasis on plants, where a specific subfamily of the proteins possessing the N-terminally positioned telobox is present in addition to more common C-terminal telobox proteins. We further demonstrate the presence of a telobox protein (CpTBP1) in Cestrum parqui, a plant lacking typical telomeres and telomerase. The protein shows nuclear localisation and association with chromatin. The role of this protein in ancestral and current telomere structure is discussed in the evolutionary context. Altogether, the present overview shows the importance of the telobox domain in a search for candidate telomere proteins but at the same time warns against oversimplified identification of any telobox protein with telomere structure without appropriate evidence of its telomeric localisation and function.
- MeSH
- Cestrum metabolismus MeSH
- DNA vazebné proteiny genetika metabolismus MeSH
- DNA metabolismus MeSH
- fylogeneze MeSH
- molekulární sekvence - údaje MeSH
- proteiny vázající telomery genetika metabolismus MeSH
- rostlinné proteiny chemie metabolismus MeSH
- sekvence aminokyselin MeSH
- telomery metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
Proteins that bind to telomeric DNA form the key structural and functional constituents of telomeres. While telomere binding proteins have been described in the majority of organisms, their identity in plants remains unknown. Several protein families containing a telomere binding motif known as the telobox have been previously described in Arabidopsis thaliana. Nonetheless, functional evidence for their involvement at telomeres has not been obtained, likely due to functional redundancy. Here we performed genetic analysis on the TRF-like family consisting of six proteins (TRB1, TRP1, TRFL1, TRFL2, TRFL4, and TRF9) which have previously shown to bind telomeric DNA in vitro. We used haploid genetics to create multiple knock-out plants deficient for all six proteins of this gene family. These plants did not exhibit changes in telomere length, or phenotypes associated with telomere dysfunction. This data demonstrates that this telobox protein family is not involved in telomere maintenance in Arabidopsis. Phylogenetic analysis in major plant lineages revealed early diversification of telobox proteins families indicating that telomere function may be associated with other telobox proteins.
- Publikační typ
- časopisecké články MeSH
Recently we characterised TRB1, a protein from a single-myb-histone family, as a structural and functional component of telomeres in Arabidopsis thaliana. TRB proteins, besides their ability to bind specifically to telomeric DNA using their N-terminally positioned myb-like domain of the same type as in human shelterin proteins TRF1 or TRF2, also possess a histone-like domain which is involved in protein-protein interactions e.g., with POT1b. Here we set out to investigate the genome-wide localization pattern of TRB1 to reveal its preferential sites of binding to chromatin in vivo and its potential functional roles in the genome-wide context. Our results demonstrate that TRB1 is preferentially associated with promoter regions of genes involved in ribosome biogenesis, in addition to its roles at telomeres. This preference coincides with the frequent occurrence of telobox motifs in the upstream regions of genes in this category, but it is not restricted to the presence of a telobox. We conclude that TRB1 shows a specific genome-wide distribution pattern which suggests its role in regulation of genes involved in biogenesis of the translational machinery, in addition to its preferential telomeric localization.
- MeSH
- Arabidopsis genetika metabolismus MeSH
- genová knihovna MeSH
- histony metabolismus MeSH
- molekulární sekvence - údaje MeSH
- nukleotidové motivy MeSH
- promotorové oblasti (genetika) genetika MeSH
- proteiny huseníčku genetika metabolismus MeSH
- proteiny vázající telomery genetika metabolismus MeSH
- proteosyntéza MeSH
- ribozomy genetika MeSH
- sekvence nukleotidů MeSH
- sekvenční analýza DNA MeSH
- sekvenční analýza hybridizací s uspořádaným souborem oligonukleotidů MeSH
- telomery metabolismus MeSH
- vazba proteinů MeSH
- výpočetní biologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Telomeres are nucleoprotein structures ensuring the stability of eukaryotic chromosome ends. Two protein families, TRFL (TFL-Like) and SMH (Single-Myb-Histone), containing a specific telobox motif in their Myb domain, have been identified as potential candidates involved in a functional nucleoprotein structure analogous to human "shelterin" at plant telomeres. We analyze the DNA-protein interaction of the full-length and truncated variants of AtTRB1, a SMH-family member with a typical structure: N-terminal Myb domain, central H1/5 domain and C-terminal coiled-coil. We show that preferential interaction of AtTRB1 with double-stranded telomeric DNA is mediated by the Myb domain, while the H1/5 domain is involved in non-specific DNA-protein interaction and in the multimerization of AtTRB1.
- MeSH
- Arabidopsis genetika metabolismus MeSH
- DNA rostlinná metabolismus MeSH
- DNA vazebné proteiny genetika metabolismus MeSH
- elektroforéza v polyakrylamidovém gelu MeSH
- financování organizované MeSH
- histony metabolismus MeSH
- klonování DNA MeSH
- lidé MeSH
- onkogenní proteiny v-myb metabolismus MeSH
- proteiny huseníčku genetika metabolismus MeSH
- telomery metabolismus MeSH
- vazba proteinů MeSH
- Check Tag
- lidé MeSH
Although telomere-binding proteins constitute an essential part of telomeres, in vivo data indicating the existence of a structure similar to mammalian shelterin complex in plants are limited. Partial characterization of a number of candidate proteins has not identified true components of plant shelterin or elucidated their functional mechanisms. Telomere repeat binding (TRB) proteins from Arabidopsis thaliana bind plant telomeric repeats through a Myb domain of the telobox type in vitro, and have been shown to interact with POT1b (Protection of telomeres 1). Here we demonstrate co-localization of TRB1 protein with telomeres in situ using fluorescence microscopy, as well as in vivo interaction using chromatin immunoprecipitation. Classification of the TRB1 protein as a component of plant telomeres is further confirmed by the observation of shortening of telomeres in knockout mutants of the trb1 gene. Moreover, TRB proteins physically interact with plant telomerase catalytic subunits. These findings integrate TRB proteins into the telomeric interactome of A. thaliana.
