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The first steps of oocyte development from primordial follicle are characterised by a growth phase, when unique RNA and protein reserves are created to achieve oocyte competence. During this growth, oocytes do not divide and the general transcription factor TATA binding protein (TBP) is replaced by its paralogue, TBPL2 (also called TBP2 or TRF3), which is essential for RNA polymerase II transcription (Pol II) 1,2 . However, the composition and function of transcription machinery and the regulatory mechanisms mediating Pol II transcription during this developmental stage remain unknown. In somatic cells, the general transcription factor TFIID, which contains TBP and 13 TBP-associated factors, is the first to bind gene promoters to nucleate Pol II transcription initiation 3 . Here, we show that in oocytes TBPL2 does not assemble into a canonical TFIID complex, while it stably associates with TFIIA via distinct TFIIA interactions when compared to TBP. Our transcript analyses in wild type and Tbpl2 -/- oocytes demonstrates that TBPL2 mediates transcription of oocyte-expressed genes, including mRNA destabilisation factors genes, as well as specific endogenous retroviral elements (ERVs). Transcription start site (TSS) mapping from wild-type and Tbpl2 -/- growing oocytes demonstrates that TBPL2 has a strong preference for TATA-like motif in gene core promoters driving specific sharp TSS selection. This is in marked contrast with TBP/TFIID-driven TATA-less gene promoters in preceding stages that have broad TSS architecture. We anticipate that our findings describing oocyte-specific transcription regulation will help to understand the mechanisms associated with primary ovarian insufficiency, which constitutes a frequent cause of infertility among women.; The first steps of oocyte development from primordial follicle are characterised by a growth phase, when unique RNA and protein reserves are created to achieve oocyte competence. During this growth, oocytes do not divide and the general transcription factor TATA binding protein (TBP) is replaced by its paralogue, TBPL2 (also called TBP2 or TRF3), which is essential for RNA polymerase II transcription (Pol II) 1,2 . However, the composition and function of transcription machinery and the regulatory mechanisms mediating Pol II transcription during this developmental stage remain unknown. In somatic cells, the general transcription factor TFIID, which contains TBP and 13 TBP-associated factors, is the first to bind gene promoters to nucleate Pol II transcription initiation 3 . Here, we show that in oocytes TBPL2 does not assemble into a canonical TFIID complex, while it stably associates with TFIIA via distinct TFIIA interactions when compared to TBP. Our transcript analyses in wild type and Tbpl2 -/- oocytes demonstrates that TBPL2 mediates transcription of oocyte-expressed genes, including mRNA destabilisation factors genes, as well as specific endogenous retroviral elements (ERVs). Transcription start site (TSS) mapping from wild-type and Tbpl2 -/- growing oocytes demonstrates that TBPL2 has a strong preference for TATA-like motif in gene core promoters driving specific sharp TSS selection. This is in marked contrast with TBP/TFIID-driven TATA-less gene promoters in preceding stages that have broad TSS architecture. We anticipate that our findings describing oocyte-specific transcription regulation will help to understand the mechanisms associated with primary ovarian insufficiency, which constitutes a frequent cause of infertility among women.

Following our recent identification of a fatty acid binding site in the SARS-CoV-2 spike protein (Toelzer et al., Science eabd3255 (2020)), we investigate the binding of linoleate and other potential ligands at this site using molecular dynamics simulations. The results support the hypothesis that linoleate stabilises the locked form of the spike, in which its interaction interface for the ACE2 receptor is occluded. The simulations indicate weaker binding of linoleate to the partially open conformation. Simulations of dexamethasone bound at this site indicate that it binds similarly to linoleate, and thus may also stabilize a locked spike conformation. In contrast, simulations suggest that cholesterol bound at this site may destabilize the locked conformation, and in the open conformation, may preferentially bind at an alternative site in the hinge region between the receptor binding domain and the domain below, which could have functional relevance. We also use molecular docking to identify potential ligands that may bind at the fatty acid binding site, using the Bristol University Docking Engine (BUDE). BUDE docking successfully reproduces the linoleate complex and also supports binding of dexamethasone at the spike fatty acid site. Virtual screening of a library of approved drugs identifies vitamins D, K and A, as well as retinoid ligands with experimentally demonstrated activity against SARS-CoV-2 replication in vitro, as also potentially able to bind at this site. Our data suggest that the fatty acid binding site of the SARS-CoV-2 spike protein may bind a diverse array of candidate ligands. Targeting this site with small molecules, including dietary components such as vitamins, which may stabilise its locked conformation and represents a potential avenue for novel therapeutics or prophylaxis for COVID-19.