Biology subjects

Pantelejevs, T.

Publications and source records attributed to Pantelejevs, T..

3 recordsLinked to original sources

bioRxiv2022

Divergent binding mode for a protozoan BRC repeat to RAD51

Interaction of BRCA2 through ca. 30 amino acid residue motifs, BRC repeats, with RAD51 is a conserved feature of the double-strand DNA break repair process in eukaryotes. In humans the binding of the eight BRC repeats is relatively well understood, with structure of BRC4 repeat bound to human RAD51 showing how two sequence motifs, FxxA and LFDE, in the BRC repeat interact with distinct sites on RAD51. Little is known however of the interaction of BRC repeats in other species, especially in protozoans where variable number of BRC repeats are found in BRCA2 proteins. Here we have studied in detail the interactions of the two BRC repeats in Leishmania infantum BRCA2 with RAD51. We show that the LiBRC1 is a high affinity repeat with a KD of 0.29 M while LiBRC2 binds to RAD51 with a KD of 13.5 M. A crystal structure of LiBRC1 complexed with LiRAD51 revels an extended {beta}-hairpin compared to human BRC4 and shows that the equivalent of human LFDE motif is not interacting with LiRAD51. A truncation analysis of LiBRC1 confirms that a shorter repeat is sufficient for high affinity interaction and this minimal repeat is functional in inhibiting the formation of LiRAD51-ssDNA nucleofilament.

biochemistry↗

bioRxiv2021

A strategy to suppress STAT1 signalling conserved in pathogenic poxviruses and paramyxoviruses

The induction of interferon-stimulated genes by signal transducer and activator of transcription (STAT) proteins, is a critical host defence to fight virus infections. Here, a highly expressed poxvirus protein 018 is shown to inhibit IFN-induced signalling by binding the SH2 domain of STAT1 to prevent STAT1 association with an activated IFN receptor. Despite the presence of additional inhibitors of IFN-induced signalling, a poxvirus lacking 018 was attenuated in mice. The 2.0 [A] crystal structure of the 018:STAT1 complex reveals a mechanism for a high-affinity, pTyr-independent mode of binding to an SH2 domain. Furthermore, the STAT1 binding motif of 018 shows sequence similarity to the STAT1-binding proteins from Nipah virus, which like 018, block the association of STAT1 with an IFN receptor. Taken together, these results provide detailed mechanistic insight into a potent mode of STAT1 antagonism, found to exist in genetically diverse virus families.

microbiology↗

bioRxiv2020

Improved RAD51 binders through motif shuffling based on the modularity of BRC repeats

Exchanges of protein sequence modules support leaps in function unavailable through point mutations during evolution. Here we study the role of the two RAD51-interacting modules within the eight binding BRC repeats of BRCA2. We created 64 chimeric repeats by shuffling these modules and measured their binding to RAD51. We found that certain shuffled repeats were stronger than any of the natural repeats, suggesting balancing of relative properties in BRC repeats. Surprisingly, the contribution from the two modules was poorly correlated with affinities of natural repeats, with weak BRC8 repeat containing the most effective N-terminal module. The binding of the strongest chimera, BRC8-2, to RAD51 was improved by -2.44 kCal/mol compared to the strongest natural repeat, BRC4. Crystal structure of RAD51:BRC8-2 complex shows an improved interface fit and an extended {beta}-hairpin in this repeat. BRC8-2 was shown to function in human cells, preventing the formation of nuclear foci after ionizing radiation.

biochemistry↗