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RAP1 at the Yeast Telomere

Wahlin, Johan LU (2002)
Abstract (Swedish)
Popular Abstract in Swedish

Det mesta av det genetiska materialet i en eukaryot cell finns samlat till kärnan och är organiserat i kromosomer. Varje gång en cell delas kopieras kromosomerna så att de båda resulterande cellerna får ett bibehållet kromosomantal. Den mekanism som styr denna replikeringsprocess förmår dock inte kopiera de yttersta kromosomändarna, vilket resulterar i att dessa blir kortare för varje celldelning. I många organismer motverkas denna förkortning av enzymet telomeras som sätter till korta DNA-sekvenser till kromosomändarna, eller telomererna som de också kallas. Vanligtvis sätter telomeras till korta TG-rika upprepningar. I människa inkorporeras t. ex. TTAGGG-upprepningar och i växten Arabidopsis... (More)
Popular Abstract in Swedish

Det mesta av det genetiska materialet i en eukaryot cell finns samlat till kärnan och är organiserat i kromosomer. Varje gång en cell delas kopieras kromosomerna så att de båda resulterande cellerna får ett bibehållet kromosomantal. Den mekanism som styr denna replikeringsprocess förmår dock inte kopiera de yttersta kromosomändarna, vilket resulterar i att dessa blir kortare för varje celldelning. I många organismer motverkas denna förkortning av enzymet telomeras som sätter till korta DNA-sekvenser till kromosomändarna, eller telomererna som de också kallas. Vanligtvis sätter telomeras till korta TG-rika upprepningar. I människa inkorporeras t. ex. TTAGGG-upprepningar och i växten Arabidopsis TTTAGGG-upprepningar. Variationen mellan telomerupprepningarna inom olika jästarter är större. De varierar i längd mellan 8 och 26 baspar, och har en heterogen nukleotidsammansättning. De innehåller dock en sekvens som liknar den till vilken RAP1 proteinet i bakjäst (Saccharomyces cerevisiae) binder. RAP1 proteinet binder med hög affinitet till telomererna och är bland annat viktigt för telomerlängdsregleringen. Vi har funnit att detta protein binder till telomera DNA-sekvenser från flera olika jästarter, vilket tyder på att dessa arter också har RAP1 proteiner bundna till sina telomerer. Dessutom fann vi att somliga av dessa sekvenser bands med en flexibilitet som dittills var okänd. Vi har identifierat två nya RAP1 homologer från jäst. De isolerades från arterna Saccharomyces castellii (scasRAP1) och Saccharomyces dairensis (sdaiRAP1). Sekvensanalyser visade att de regioner som är viktiga för funktionen av proteinet i S. cerevisiae (scerRAP1) var väl konserverade i homologerna. Homologernas inbindningsegenskaper till olika telomera sekvenser var också liknande scerRAP1 proteinets. Till skillnad från scerRap1p band de dock till telomera upprepning från människa. Vi fann att scasRAP1-genen kan ersätta scerRAP1-genen i en S. cerevisiae-stam. Telomererna i en sådan hybridstam var längre och mer heterogena än i vildtypsstammen. Vi satte in S. castellii telomera sekvenser i en S. cerevisiae-telomer och fann att denna förkortades med en sträcka som nästan motsvarade den som S. castellii-sekvensen utgjorde. Detta tyder på att S. castellii-upprepningarna räknas som en del av telomeren. Sammantaget har våra resultat ökat kunskapen om RAP1-proteinet som har stor betydelse för en rad olika funktioner i jäst. (Less)
Abstract
Telomeres are specialized complexes of DNA and proteins that cap and confer stability to the ends of eukaryotic chromosomes. The telomeric DNA of most eukaryotes is composed of tandemly arranged short repeats. Within the budding yeasts these repeats are diverged in length as well as in nucleotide composition. However, they contain a sequence resembling the consensus binding sequence of the major telomere-binding protein Repressor Activator Protein 1 (Rap1p). It is shown here that the telomeric repeat units of several budding yeasts are indeed bound by the Saccharomyces cerevisiae RAP1 protein(scerRap1p) in vitro. Furthermore, the protein can bind to some of those sequences with spatial flexibility. The identification of two novel RAP1... (More)
Telomeres are specialized complexes of DNA and proteins that cap and confer stability to the ends of eukaryotic chromosomes. The telomeric DNA of most eukaryotes is composed of tandemly arranged short repeats. Within the budding yeasts these repeats are diverged in length as well as in nucleotide composition. However, they contain a sequence resembling the consensus binding sequence of the major telomere-binding protein Repressor Activator Protein 1 (Rap1p). It is shown here that the telomeric repeat units of several budding yeasts are indeed bound by the Saccharomyces cerevisiae RAP1 protein(scerRap1p) in vitro. Furthermore, the protein can bind to some of those sequences with spatial flexibility. The identification of two novel RAP1 homologues are also presented here. They were isolated from Saccharomyces castellii (scasRAP1) and Saccharomyces dairensis (sdaiRAP1). Sequence analyses revealed that the DNA-binding and C-terminal domains of these proteins are similar to the corresponding regions of scerRap1p, reflecting the importance of these regions in the function of the protein. The similarity between the proteins is underscored by the finding that the scasRAP1 gene can replace the scerRAP1 gene in a S. cerevisiae strain. Binding analyses revealed that the scas- and sdaiRAP1 proteins bind to telomeric sequences in a similar manner as scerRap1p. However unlike scerRap1p, these proteins can bind to the telomeric repeats of vertebrates in vitro. It is shown here that telomeric repeats from S. castellii/S. dairensis introduced into a S. cerevisiae telomere are sensed as being part of the telomere by the telomere length sensing mechanism. Such hybrid telomeres are kept at slightly shorter lengths than telomeres containing S. cerevisiae telomeric DNA only. Since these S. castellii/S. dairensis telomeric repeats have a denser distribution of Rap1p binding sites than S. cerevisiae telomeric DNA, this shortening of the telomeric tracts would be predicted from the RAP1 protein counting model of telomere length regulation. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr Lingner, Joachim, Switzerland
organization
publishing date
type
Thesis
publication status
published
subject
keywords
cytogenetik, DNA-binding, Saccharomyces, yeast, telomeric repeat, telomere, RAP1, repressor activator protein 1, Genetics, cytogenetics, Genetik
pages
140 pages
publisher
Johan Wahlin, Dep. of Cell and Organism Biology, Sölvegatan 29, 223 62 Lund, Sweden,
defense location
Sölvegatan 29, Lund
defense date
2002-06-01 10:15
ISBN
91-628-5256-6
language
English
LU publication?
yes
id
ff8574c9-1fd6-49ad-b334-59a20ad35b1e (old id 464700)
date added to LUP
2007-09-07 11:25:55
date last changed
2016-09-19 08:45:10
@misc{ff8574c9-1fd6-49ad-b334-59a20ad35b1e,
  abstract     = {Telomeres are specialized complexes of DNA and proteins that cap and confer stability to the ends of eukaryotic chromosomes. The telomeric DNA of most eukaryotes is composed of tandemly arranged short repeats. Within the budding yeasts these repeats are diverged in length as well as in nucleotide composition. However, they contain a sequence resembling the consensus binding sequence of the major telomere-binding protein Repressor Activator Protein 1 (Rap1p). It is shown here that the telomeric repeat units of several budding yeasts are indeed bound by the Saccharomyces cerevisiae RAP1 protein(scerRap1p) in vitro. Furthermore, the protein can bind to some of those sequences with spatial flexibility. The identification of two novel RAP1 homologues are also presented here. They were isolated from Saccharomyces castellii (scasRAP1) and Saccharomyces dairensis (sdaiRAP1). Sequence analyses revealed that the DNA-binding and C-terminal domains of these proteins are similar to the corresponding regions of scerRap1p, reflecting the importance of these regions in the function of the protein. The similarity between the proteins is underscored by the finding that the scasRAP1 gene can replace the scerRAP1 gene in a S. cerevisiae strain. Binding analyses revealed that the scas- and sdaiRAP1 proteins bind to telomeric sequences in a similar manner as scerRap1p. However unlike scerRap1p, these proteins can bind to the telomeric repeats of vertebrates in vitro. It is shown here that telomeric repeats from S. castellii/S. dairensis introduced into a S. cerevisiae telomere are sensed as being part of the telomere by the telomere length sensing mechanism. Such hybrid telomeres are kept at slightly shorter lengths than telomeres containing S. cerevisiae telomeric DNA only. Since these S. castellii/S. dairensis telomeric repeats have a denser distribution of Rap1p binding sites than S. cerevisiae telomeric DNA, this shortening of the telomeric tracts would be predicted from the RAP1 protein counting model of telomere length regulation.},
  author       = {Wahlin, Johan},
  isbn         = {91-628-5256-6},
  keyword      = {cytogenetik,DNA-binding,Saccharomyces,yeast,telomeric repeat,telomere,RAP1,repressor activator protein 1,Genetics,cytogenetics,Genetik},
  language     = {eng},
  pages        = {140},
  publisher    = {ARRAY(0x94baa48)},
  title        = {RAP1 at the Yeast Telomere},
  year         = {2002},
}