ATXN3 controls DNA replication and transcription by regulating chromatin structure

The deubiquitinating enzyme Ataxin-3 (ATXN3) contains a polyglutamine (PolyQ) region, the expansion of which causes spinocerebellar ataxia type-3 (SCA3). ATXN3 has multiple functions, such as regulating transcription or controlling genomic stability after DNA damage. Here we report the role of ATXN3 in chromatin organization during unperturbed conditions, in a catalytic-independent manner. The lack of ATXN3 leads to abnormalities in nuclear and nucleolar morphology, alters DNA replication timing and increases transcription. Additionally, indicators of more open chromatin, such as increased mobility of histone H1, changes in epigenetic marks and higher sensitivity to micrococcal nuclease digestion were detected in the absence of ATXN3. Interestingly, the effects observed in cells lacking ATXN3 are epistatic to the inhibition or lack of the histone deacetylase 3 (HDAC3), an interaction partner of ATXN3. The absence of ATXN3 decreases the recruitment of endogenous HDAC3 to the chromatin, as well as the HDAC3 nuclear/cytoplasm ratio after HDAC3 overexpression, suggesting that ATXN3 controls the subcellular localization of HDAC3. Importantly, the overexpression of a PolyQ-expanded version of ATXN3 behaves as a null mutant, altering DNA replication parameters, epigenetic marks and the subcellular distribution of HDAC3, giving new insights into the molecular basis of the disease.</p

ATXN3 controls DNA replication and transcription by regulating chromatin structure

The deubiquitinating enzyme Ataxin-3 (ATXN3) contains a polyglutamine (PolyQ) region, the expansion of which causes spinocerebellar ataxia type-3 (SCA3). ATXN3 has multiple functions, such as regulating transcription or controlling genomic stability after DNA damage. Here we report the role of ATXN3 in chromatin organization during unperturbed conditions, in a catalytic-independent manner. The lack of ATXN3 leads to abnormalities in nuclear and nucleolar morphology, alters DNA replication timing and increases transcription. Additionally, indicators of more open chromatin, such as increased mobility of histone H1, changes in epigenetic marks and higher sensitivity to micrococcal nuclease digestion were detected in the absence of ATXN3. Interestingly, the effects observed in cells lacking ATXN3 are epistatic to the inhibition or lack of the histone deacetylase 3 (HDAC3), an interaction partner of ATXN3. The absence of ATXN3 decreases the recruitment of endogenous HDAC3 to the chromatin, as well as the HDAC3 nuclear/cytoplasm ratio after HDAC3 overexpression, suggesting that ATXN3 controls the subcellular localization of HDAC3. Importantly, the overexpression of a PolyQ-expanded version of ATXN3 behaves as a null mutant, altering DNA replication parameters, epigenetic marks and the subcellular distribution of HDAC3, giving new insights into the molecular basis of the disease.Spanish Agencia Estatal de Investigacion´ [PID2019- 109222RB-I00/AEI/10.13039/501100011033]; European Union Regional Funds (FEDER) (to R.F., V.A.J.S.); Agencia Canaria de Investigacion, ´ Innovacion´ y Sociedad de la Informacion´ [ProID2020010109]; FEDER (to R.F.); Agencia Canaria de Investigacion, ´ Innovacion´ y European Social Fund integrated Operational programme of the Canary Islands Sociedad de la Informacion´ de la Consejer´ıa de Econom´ıa, Industria, Comercio y Conocimiento and the 2014–2020, Eje 3 Tema Prioritario 74 (85%) (to E.H.C.); Medical Research Council Programme [MR/X006409/1 to K.R.]; Breast Cancer Now [2019DecPR1406 to K.R.]. Funding for open access charge: Agencia Canaria de Investigacion, ´ Innovacion´ y Sociedad de la Informacion´ [ProID2020010109]; European Union Regional Funds (FEDER)

Izaña Atmospheric Research Center. Activity Report 2015-2016

This report is a summary of the many activities at the Izaña Atmospheric Research Center to the broader community. The combination of operational activities, research and development in state-of-the-art measurement techniques, calibration and validation and international cooperation encompass the vision of WMO to provide world leadership in expertise and international cooperation in weather, climate, hydrology and related environmental issues

Identificación del rol de USP37 como una hidrolasa de ubiquitina de la subunidad M2 de la ribonucleótido reductasa (RRM2) y otros sustratos

USP37 es una hidrolasa de ubiquitina importante para el control del ciclo celular promoviendo específicamente la transición desde la fase G1 a S del ciclo celular. Para ello esta enzima cataliza la hidrólisis de los enlaces peptídicos entre la ubiquitina y varias proteínas como Ciclina A, previniendo su degradación. Los niveles de USP37 son controlados por el complejo APC/Cdh1 durante el ciclo celular, permanecen bajos en la fase G1 del ciclo celular mientras que son altos durante las fases S y G2. La enzima Ribonucleótido reductasa (RR) cataliza la reducción de ribonucleótidos a desoxirribonucleótidos y por lo tanto es necesaria para la síntesis de ADN, por ejemplo, durante la replicación y reparación del ADN. RR está formada por dos subunidades y su actividad está altamente regulada a través de la ubiquitinación y degradación por proteasoma de la subunidad RRM2 (subunidad M2 de la ribonucleótido reductasa). Mus81 es una endonucleasa de ADN cuyo papel ha sido descrito como esencial en la recombinación homóloga y cuya actividad está controlada durante la replicación del ADN. Datos preliminares y sin publicar del laboratorio indican que USP37 puede regular a RRM2 y Mus81. En este proyecto, nos propusimos caracterizar el papel de USP37 controlando a RRM2 y Mus81. Para ello, se sobreexpresó e inhibió a USP37 y los niveles de RRM2 y Mus81 fueron estudiados. También llevamos a cabo estudios de interacción a través de coinmunoprecipitaciones y en el caso de RRM2, estudiamos los niveles de ubiquitinación después de sobreexpresar USP37. En general, los resultados de nuestro estudio sugieren que RRM2 y Mus81 no son dianas principales de USP37.USP37 is a ubiquitin hydrolase important for cell cycle control that specifically promotes the transition from G1 to S phases of the cell cycle. For that this enzyme catalyses the hydrolysis of peptide bonds between ubiquitin and several proteins such as Cyclin A preventing its degradation. USP37 levels are controlled by APC/Cdh1 complex during the cell cycle: they remain low in the G1 phase of the cell cycle while they are high during S and G2 phases. The Ribonucleotide reductase enzyme (RR) catalyses the reduction of ribonucleotides to deoxyribonucleotides and therefore is required for DNA synthesis, for example during DNA replication and DNA repair. RR is formed by two subunits and its activity is tightly regulated by ubiquitin dependent proteasomal degradation of the so called RRM2 subunit (ribonucleotide reductase M2 subunit). Mus81 is a structure specific DNA endonuclease whose role was previously shown to be essential during homologous recombination and is regulated during DNA replication. Preliminary unpublished data from the laboratory indicate that USP37 can regulate RRM2 and Mus81. In this project, we aimed to characterize the role of USP37 controlling RRM2 and Mus81. For that, we overexpressed and downregulated USP37 and studied the levels of both proteins. We also performed interaction studies by co-immunoprecipitations and in the case of RRM2, we studied the ubiquitination levels after USP37 overexpression. Overall, the results of our study suggest that RRM2 and Mus81 are not major targets of USP37. Key Words: USP37, RRM2, Mus81, ubiquitin, de-ubiquitination, DUB, R

Izaña Atmospheric Research Center. Activity Report 2012-2014

This report is a summary of the many activities at the Izaña Atmospheric Research Center to the broader community. The combination of operational activities, research and development in state-of-the-art measurement techniques, calibration and validation and international cooperation encompass the vision of WMO to provide world leadership in expertise and international cooperation in weather, climate, hydrology and related environmental issues