Saccharomyces cerevisiae Rap1-interacting factor 1 CTD domain, metazoan Rif1 C-II domains and related domains
This model includes Saccharomyces cerevisiae Rif1_CTD (carboxy-terminal domain) and metazoan Rif1 C-II (C-terminal subdomain II). Rif1 was originally identified in S. cerevisiae where it negatively regulates telomere length homeostasis via interaction with the C-terminal domain of Rap1. A protective capping structure (telosome) comprised of Rap1, Rif1, and Rif2, inhibits telomerase, counteracts SIR-mediated transcriptional silencing, and prevents inadvertent recognition of telomeres as DNA double-strand breaks (DSBs). S. cerevisiae Rif1 has two Rap1 binding sites: the Rap1-binding module (RBM), and the CTD domain. The latter, represented here, has a lower Rap1 affinity, and provides trans binding through tetramerization. In mammals, Rif1 has been implicated in various cellular processes including pluripotency of stem cells, breast cancer development, and DSB repair pathway choice. A mutual antagonism between the nonhomologous end joining factors (53BP1-RIF1) and the homologous recombination factors (BRCA1 -CtIP) ensures correct repair pathway choice.
Comment:based on yeast Rif1-CTD which provides trans binding of Rap1 at telomeres through tetramerization; however, its telomeric role may not be conserved.
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