%0 Journal Article %J Mol Neurobiol %D 2022 %T Function of FMRP Domains in Regulating Distinct Roles of Neuronal Protein Synthesis. %A D'Souza, Michelle Ninochka %A Ramakrishna, Sarayu %A Radhakrishna, Bindushree K %A Jhaveri, Vishwaja %A Ravindran, Sreenath %A Yeramala, Lahari %A Nair, Deepak %A Palakodeti, Dasaradhi %A Muddashetty, Ravi S %K Fragile X Mental Retardation Protein %K Fragile X Syndrome %K Humans %K Microtubules %K Neurons %K Protein Biosynthesis %K Ribosomes %K RNA, Messenger %X

The Fragile-X Mental Retardation Protein (FMRP) is an RNA binding protein that regulates translation of mRNAs essential for synaptic development and plasticity. FMRP interacts with a specific set of mRNAs, aids in their microtubule-dependent transport and regulates their translation through its association with ribosomes. However, the biochemical role of FMRP's domains in forming neuronal granules and associating with microtubules and ribosomes is currently undefined. We report that the C-terminus domain of FMRP is sufficient to bind to ribosomes akin to the full-length protein. Furthermore, the C-terminus domain alone is essential and responsible for FMRP-mediated neuronal translation repression. However, dendritic distribution of FMRP and its microtubule association is favored by the synergistic combination of FMRP domains rather than individual domains. Interestingly, we show that the phosphorylation of hFMRP at Serine-500 is important in modulating the dynamics of translation by controlling ribosome association. This is a fundamental mechanism governing the size and number of FMRP puncta that contain actively translating ribosomes. Finally through the use of pathogenic mutations, we emphasize the hierarchical contribution of FMRP's domains in translation regulation.

%B Mol Neurobiol %V 59 %P 7370-7392 %8 2022 Dec %G eng %N 12 %R 10.1007/s12035-022-03049-1 %0 Journal Article %J Elife %D 2021 %T Duox generated reactive oxygen species activate ATR/Chk1 to induce G2 arrest in tracheoblasts. %A Kizhedathu, Amrutha %A Chhajed, Piyush %A Yeramala, Lahari %A Sain Basu, Deblina %A Mukherjee, Tina %A Vinothkumar, Kutti R %A Guha, Arjun %X

Progenitors of the thoracic tracheal system of adult (tracheoblasts) arrest in G2 during larval life and rekindle a mitotic program subsequently. G2 arrest is dependent on ATR-dependent phosphorylation of Chk1 that is actuated in the absence of detectable DNA damage. We are interested in the mechanisms that activate ATR/Chk1 (Kizhedathu et al., 2018, 2020). Here we report that levels of reactive oxygen species (ROS) are high in arrested tracheoblasts and decrease upon mitotic re-entry. High ROS is dependent on expression of Duox, an HO generating-Dual Oxidase. ROS quenching by overexpression of Superoxide Dismutase 1, or by knockdown of Duox, abolishes Chk1 phosphorylation and results in precocious proliferation. Tracheae deficient in Duox, or deficient in both Duox and regulators of DNA damage-dependent ATR/Chk1 activation (ATRIP/TOPBP1/ Claspin), can induce phosphorylation of Chk1 in response to micromolar concentrations of HO in minutes. The findings presented reveal that HO activates ATR/Chk1 in tracheoblasts by a non-canonical, potentially direct, mechanism.

%B Elife %V 10 %8 2021 Oct 08 %G eng %R 10.7554/eLife.68636