Biology subjects

Reddy, P. P.

Publications and source records attributed to Reddy, P. P..

3 recordsLinked to original sources

bioRxiv2024

Structural analysis of genetic variants of the human tumor suppressor Palb2 coiled-coil domain

Homologous recombination (HR) is an obligate pathway to repair DNA lesions and maintain genome integrity. The tumor suppressor Palb2 is an integral part of the HR pathway that functionally connects BRCA proteins at the site of DNA damage. The N-terminal coiled-coil domain in Palb2 switches from an inactive to an active complex during HR. In the inactive form, Palb2 forms homodimers, and during HR, it assumes the active state, forming a heterodimeric complex with BRCA1. However, the structural details of the human Palb2 coiled-coil domain are unknown. About 600 missense variants have been reported in Palb2, and several are in the coiled-coil domain. The structure-function relationship of such variants is poorly understood, which challenges genetic counseling. Here, we report the solution structure of the human Palb2 coiled-coil domain, which forms an antiparallel homodimer. We then use the structure to study the effect of a few well-characterized missense mutations on the fold and interactions of the Palb2 coiled-coil domain. The structural impact of mutations correlates excellently with their efficiency in homologous recombination, signifying that the approach can be exploited to study other genetic variations in the Palb2.

biophysics↗

bioRxiv2020

Genetically encoded live cell sensor for tyrosinated microtubules

Microtubule cytoskeleton exists in various biochemical forms in different cells due to tubulin post-translational modification (PTMs). These PTMs are known to affect microtubule stability, dynamics and interaction with MAPs and motors in a specific manner, widely known as tubulin code hypothesis. At present there exist no tool that can specifically mark tubulin PTMs in live cells, thus severely limiting our understanding of tubulin PTMs. Using yeast display library, we identified a binder against terminal tyrosine of alpha tubulin, a unique PTM site. Extensive characterization validates the robustness and non-perturbing nature of our binder as tyrosination sensor, a live cell tubulin nanobody specific towards tyrosinated or unmodified microtubules. Using which, in real time we followed nocodazole, colchicine and vincristine induced depolymerization events of unmodified microtubules, and found each distinctly perturb microtubule polymer. Together, our work describes the tyrosination sensor and potential applications to study microtubule and PTM processes in living cells.

cell biology↗

bioRxiv2019

A novel polyubiquitin chain linkage formed by viral Ubiquitin prevents cleavage by deubiquitinating enzymes

The Baculoviridae family of viruses encode a viral Ubiquitin gene. Although the viral Ubiquitin is homologous to eukaryotic Ubiquitin (Ub), preservation of this gene in the viral genome indicates a unique function that is absent in the host eukaryotic Ub. We report the structural, biophysical, and biochemical properties of the viral Ubiquitin from Autographa Californica Multiple Nucleo-Polyhedrosis Virus (AcMNPV). The structure of viral Ubiquitin (vUb) differs from Ub in the packing of the central helix 1 to the beta-sheet of the {beta}-grasp fold. Consequently, the stability of the fold is lower in vUb compared to Ub. However, the surface properties, ubiquitination activity, and the interaction with Ubiquitin binding domains are similar between vUb and Ub. Interestingly, vUb forms atypical polyubiquitin chain linked by lysine at the 54th position (K54). The K54-linked polyubiquitin chains are neither effectively cleaved by deubiquitinating enzymes, nor are they targeted by proteasomal degradation. We propose that modification of proteins with the viral Ubiquitin is a mechanism to counter the host antiviral responses.

biochemistry↗