gocentral
commented
15 years ago OK, I've edited the definition. I think it does fit the definition of telomere cap complex, though -- it meets all the criteria, and adds more features, so it's ontologically sound.
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Original comment by: mah11
I think Shelterin needs updating slightly. See correspondence with Miguel Ferreira below:
You're completely right. Shelterin involves both ss and ds telomere complexes.
In fact, they appear to be intimately connected. Not only by DNA- protein interaction, but also through protein-protein interaction. Meaning: You may well get Pot1/Tpz1 (ie, a ssDNA protein) at the dsDNA region via a Poz1 "bridge" that connects them to Taz1/Rap1 (dsDNA).
But, I think your definition is not that far off.
>> A nuclear telomere cap complex that is formed by the association of >> the shelterin protein (POT1 or a homolog thereof) and several other >> proteins with telomeric DNA. The complex contains TRF1, TRF2, POT1, >> RAP1, TIN2 and TPP1 in mammalian cells, and Pot1, Tpz1, Ccq1, Poz1, >> and Rap1 in Schizosaccharomyces
It is just that the whole complex is called "shelterin" rather than possessing a "shelterin" protein. In fact, you could just say that the shelterin complex is comprised of Taz1/Rap1proteins that bind ds- telomere DNA and of Pot1/Tpz1 proteins that bind the ss-telomere region and that both subcomplexes can be bridged via Poz1.
In fission yeast, both these subcomplexes possess additional components relative to their human counterparts: the Pot1/Tpz1 further interact with Ccq1 and Taz1 binds to Rif1. But I would not immediately count them as shelterin. The reason is that this name was given to an experimentally purified telomere complex purified from cells. As Titia de Lange said, there may be many more proteins interacting with shelterin but these six (in humans) are stoichiometric.
Just one more thing... I would not simply call it telomere "cap". They work for protection (as the name suggests) but they are also responsible for recruiting telomerase. So, maybe I would just call it telomere complex required for chromosome-end protection and telomerase recruitment.
I hope this helps... Best wishes, Miguel
Reported by: ValWood
Original Ticket: geneontology/ontology-requests/6290