Bipartite Role of Hsp90 Keeps CRAF Kinase Poised for Activation [Protein Structure and Folding]

October 5th, 2016 by Mitra, S., Ghosh, B., Gayen, N., Roy, J., Mandal, A. K.

CRAF kinase maintains cell viability, growth and proliferation by participating in MAPK pathway. Unlike BRAF, CRAF requires continuous chaperoning by Hsp90 to retain MAPK signaling. But, the reason behind the continuous association of Hsp90 with CRAF is still elusive. In this study, we have identified the bipartite role of Hsp90 in chaperoning CRAF kinase. Hsp90 facilitates Ser-621 phosphorylation of CRAF and prevents the kinase from degradation. Co-chaperone Cdc37 assists in this phosphorylation event. However, after folding the stability of the kinase becomes insensitive to Hsp90 inhibition, although the physical association between Hsp90 and CRAF remains intact. We observe that over-expression of Hsp90 stimulates MAPK signaling by activating CRAF. The interaction between Hsp90 and CRAF is substantially increased under elevated level of cellular Hsp90 and in presence of either active Ras (RasV12) or EGF. Surprisingly, enhanced binding of Hsp90 to CRAF occurs prior to the Ras-CRAF association and facilitates actin recruitment to CRAF for efficient Ras-CRAF interaction, which is independent of Hsp90s ATPase activity. However, monomeric CRAF (CRAF R401H) shows abrogated interaction with both Hsp90 and actin, thereby affecting Hsp90-dependent CRAF activation. This finding suggests that stringent assemblage of Hsp90 keeps CRAF kinase equipped for participating in MAPK pathway. Thus, the role of Hsp90 in CRAF maturation and activation acts as a limiting factor to maintain the function of a strong client like CRAF kinase.

Functional mining of transporters using synthetic selections

October 3rd, 2016 by Hans J Genee

Nature Chemical Biology 12, 1015 (2016). doi:10.1038/nchembio.2189

Authors: Hans J Genee, Anne P Bali, Søren D Petersen, Solvej Siedler, Mads T Bonde, Luisa S Gronenberg, Mette Kristensen, Scott J Harrison & Morten O A Sommer

Polyketide and nonribosomal peptide retro-biosynthesis and global gene cluster matching

October 3rd, 2016 by Chris A Dejong

Nature Chemical Biology 12, 1007 (2016). doi:10.1038/nchembio.2188

Authors: Chris A Dejong, Gregory M Chen, Haoxin Li, Chad W Johnston, Mclean R Edwards, Philip N Rees, Michael A Skinnider, Andrew L H Webster & Nathan A Magarvey

  • Posted in Nat Chem Biol, Publications
  • Comments Off on Polyketide and nonribosomal peptide retro-biosynthesis and global gene cluster matching

Enzymatic hydrolysis by transition-metal-dependent nucleophilic aromatic substitution

October 3rd, 2016 by Sibel Kalyoncu

Nature Chemical Biology 12, 1031 (2016). doi:10.1038/nchembio.2191

Authors: Sibel Kalyoncu, David P Heaner, Zohre Kurt, Casey M Bethel, Chiamaka U Ukachukwu, Srinivas Chakravarthy, Jim C Spain & Raquel L Lieberman

  • Posted in Nat Chem Biol, Publications
  • Comments Off on Enzymatic hydrolysis by transition-metal-dependent nucleophilic aromatic substitution

Cbr1 is a Dph3 reductase required for the tRNA wobble uridine modification

October 3rd, 2016 by Zhewang Lin

Nature Chemical Biology 12, 995 (2016). doi:10.1038/nchembio.2190

Authors: Zhewang Lin, Min Dong, Yugang Zhang, Eunyoung Alisa Lee & Hening Lin

Diphthamide and the tRNA wobble uridine modifications both require diphthamide biosynthesis 3 (Dph3) protein as an electron donor for the iron-sulfur clusters in their biosynthetic enzymes. Here, using a proteomic approach, we identified Saccharomyces cerevisiae cytochrome b5 reductase (Cbr1) as a NADH-dependent reductase for Dph3. The NADH- and Cbr1-dependent reduction of Dph3 may provide a regulatory linkage between cellular metabolic state and protein translation.

  • Posted in Nat Chem Biol, Publications
  • Comments Off on Cbr1 is a Dph3 reductase required for the tRNA wobble uridine modification

Oligosaccharyltransferase inhibition induces senescence in RTK-driven tumor cells

October 3rd, 2016 by Cecilia Lopez-Sambrooks

Nature Chemical Biology 12, 1023 (2016). doi:10.1038/nchembio.2194

Authors: Cecilia Lopez-Sambrooks, Shiteshu Shrimal, Carol Khodier, Daniel P Flaherty, Natalie Rinis, Jonathan C Charest, Ningguo Gao, Peng Zhao, Lance Wells, Timothy A Lewis, Mark A Lehrman, Reid Gilmore, Jennifer E Golden & Joseph N Contessa

  • Posted in Nat Chem Biol, Publications
  • Comments Off on Oligosaccharyltransferase inhibition induces senescence in RTK-driven tumor cells

The AAA+ FtsH Protease Degrades an ssrA-Tagged Model Protein in the Inner Membrane of Escherichia coli

September 30th, 2016 by Sanjay B. Hari and Robert T. Sauer

TOC Graphic

Biochemistry
DOI: 10.1021/acs.biochem.6b00920

Roger Y. Tsien 1952–2016

September 26th, 2016 by Amy E Palmer

Nature Chemical Biology 12, 887 (2016). doi:10.1038/nchembio.2213

Authors: Amy E Palmer & Jin Zhang

Roger Tsien left us on August 24. His untimely passing has saddened and shocked the scientific community. Roger literally and figuratively brightened our world, illuminated the dark matter of biology, and forever changed our view of the interface of chemistry and biology.

Structural basis for precursor protein–directed ribosomal peptide macrocyclization

September 26th, 2016 by Kunhua Li

Nature Chemical Biology 12, 973 (2016). doi:10.1038/nchembio.2200

Authors: Kunhua Li, Heather L Condurso, Gengnan Li, Yousong Ding & Steven D Bruner

  • Posted in Nat Chem Biol, Publications
  • Comments Off on Structural basis for precursor protein–directed ribosomal peptide macrocyclization

Thermal profiling reveals phenylalanine hydroxylase as an off-target of panobinostat

September 26th, 2016 by Isabelle Becher

Nature Chemical Biology 12, 908 (2016). doi:10.1038/nchembio.2185

Authors: Isabelle Becher, Thilo Werner, Carola Doce, Esther A Zaal, Ina Tögel, Crystal A Khan, Anne Rueger, Marcel Muelbaier, Elsa Salzer, Celia R Berkers, Paul F Fitzpatrick, Marcus Bantscheff & Mikhail M Savitski

We describe a two-dimensional thermal proteome profiling strategy that can be combined with an orthogonal chemoproteomics approach to enable comprehensive target profiling of the marketed histone deacetylase inhibitor panobinostat. The N-hydroxycinnamide moiety is identified as critical for potent and tetrahydrobiopterin-competitive inhibition of phenylalanine hydroxylase leading to increases in phenylalanine and decreases in tyrosine levels. These findings provide a rationale for adverse clinical observations and suggest repurposing of the drug for treatment of tyrosinemia.

  • Posted in Nat Chem Biol, Publications
  • Comments Off on Thermal profiling reveals phenylalanine hydroxylase as an off-target of panobinostat