Structural basis for recruitment of the CHK1 DNA damage kinase by the CLASPIN scaffold protein.

CHK1 is a protein kinase that functions downstream of activated ATR to phosphorylate multiple targets as part of intra-S and G2/M DNA damage checkpoints. Its role in allowing cells to survive replicative stress has made it an important target for anti-cancer drug discovery. Activation of CHK1 by ATR depends on their mutual interaction with CLASPIN, a natively unstructured protein that interacts with CHK1 through a cluster of phosphorylation sites in its C-terminal half.

Structural basis for phosphorylation-dependent recruitment of Tel2 to Hsp90 by Pih1.

Client protein recruitment to the Hsp90 system depends on cochaperones that bind the client and Hsp90 simultaneously and facilitate their interaction. Hsp90 involvement in the assembly of snoRNPs, RNA polymerases, PI3-kinase-like kinases, and chromatin remodeling complexes depends on the TTT (Tel2-Tti1-Tti2), and R2TP complexes-consisting of the AAA-ATPases Rvb1 and Rvb2, Tah1 (Spagh/RPAP3 in metazoa), and Pih1 (Pih1D1 in humans)-that together provide the connection to Hsp90. The biochemistry underlying R2TP function is still poorly understood.

Synthesis of macrolactam analogues of radicicol and their binding to heat shock protein Hsp90.

A series of macrolactam analogues of the naturally occurring resorcylic acid lactone radicicol have been synthesised from methyl orsellinate in 7 steps, involving chlorination, protection of the two phenolic groups, and hydrolysis to the benzoic acid. Formation of the dianion and quenching with a Weinreb amide results in acylation of the toluene methyl group that is followed by amide formation and ring closing metathesis to form the macrocyclic lactam. Final deprotection of the phenolic groups gives the desired macrolactams whose binding to the N-terminal domain of yeast Hsp90 was studied by isothermal titration calorimetry and protein X-ray crystallography.