Browsing by Subject "MULTIPLE DELETIONS"

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  • Euro, Liliya; Haapanen, Outi; Rog, Tomasz; Vattulainen, Ilpo; Suomalainen, Anu; Sharma, Vivek (2017)
    DNA polymerase gamma (Pol gamma) is a key component of the mitochondrial DNA replisome and an important cause of neurological diseases. Despite the availability of its crystal structures, the molecular mechanism of DNA replication, the switch between polymerase and exonuclease activities, the site of replisomal interactions, and functional effects of patient mutations that do not affect direct catalysis have remained elusive. Here we report the first atomistic classical molecular dynamics simulations of the human Pol gamma replicative complex. Our simulation data show that DNA binding triggers remarkable changes in the enzyme structure, including (1) completion of the DNA-binding channel via a dynamic subdomain, which in the apo form blocks the catalytic site, (2) stabilization of the structure through the distal accessory beta-subunit, and (3) formation of a putative transient replisome-binding platform in the "intrinsic processivity" subdomain of the enzyme. Our data indicate that noncatalytic mutations may disrupt replisomal interactions, thereby causing Pol gamma-associated neurodegenerative disorders.
  • Khan, Nahid A.; Auranen, Mari; Paetau, Ilse; Pirinen, Eija; Euro, Liliya; Forsström, Saara; Pasila, Lotta; Velagapudi, Vidya; Carroll, Christopher J.; Auwerx, Johan; Suomalainen, Anu (2014)
  • Forsström, Saara; Jackson, Christopher B.; Carroll, Christopher J.; Kuronen, Mervi; Pirinen, Eija; Pradhan, Swagat; Marmyleva, Anastasiia; Auranen, Mari; Kleine, Iida-Marja; Khan, Nahid A.; Roivainen, Anne; Marjamäki, Paivi; Liljenbäck, Heidi; Wang, Liya; Battersby, Brendan J.; Richter, Uwe; Velagapudi, Vidya; Nikkanen, Joni; Euro, Liliya; Suomalainen, Anu (2019)
    Mitochondrial dysfunction elicits stress responses that safeguard cellular homeostasis against metabolic insults. Mitochondrial integrated stress response (ISRmt) is a major response to mitochondrial (mt)DNA expression stress (mtDNA maintenance, translation defects), but the knowledge of dynamics or interdependence of components is lacking. We report that in mitochondrial myopathy, ISRmt progresses in temporal stages and development from early to chronic and is regulated by autocrine and endocrine effects of FGF21, a metabolic hormone with pleiotropic effects. Initial disease signs induce transcriptional ISRmt (ATF5, mitochondria) one-carbon cycle, FGF21, and GDF15). The local progression to 2nd metabolic ISRmt stage (ATF3, ATF4, glucose uptake, serine biosynthesis, and transsulfuration) is FGF21 dependent. Mitochondria! unfolded protein response marks the 3rd ISRmt stage of failing tissue. Systemically, FGF21 drives weight loss and glucose preference, and modifies metabolism and respiratory chain deficiency in a specific hippocampal brain region. Our evidence indicates that FGF21 is a local and systemic messenger of mtDNA stress in mice and humans with mitochondrial disease.
  • Pirinen, Eija; Auranen, Mari; Khan, Nahid A.; Brilhante, Virginia; Urho, Niina; Pessia, Alberto; Hakkarainen, Antti; Kuula, Juho; Heinonen, Ulla; Schmidt, Mark S.; Haimilahti, Kimmo; Piirilä, Päivi; Lundbom, Nina; Taskinen, Marja-Riitta; Brenner, Charles; Velagapudi, Vidya; Pietiläinen, Kirsi H.; Suomalainen, Anu (2020)
    NAD(+) is a redox-active metabolite, the depletion of which has been proposed to promote aging and degenerative diseases in rodents. However, whether NAD(+) depletion occurs in patients with degenerative disorders and whether NAD(+) repletion improves their symptoms has remained open. Here, we report systemic NAD(+) deficiency in adult-onset mitochondrial myopathy patients. We administered an increasing dose of NAD(+) booster niacin, a vitamin B3 form (to 750-1,000 mg/day; NCT03973203) for patients and their matched controls for 10 or 4 months, respectively. Blood NAD(+) increased in all subjects, up to 8-fold, and muscle-NAD(+) of patients reached the level of their controls. Some patients showed anemia tendency, while muscle strength and mitochondrial biogenesis increased in all subjects. In patients, muscle metabolome shifted toward controls and liver fat decreased even 50%. Our evidence indicates that blood analysis is useful in identifying NAD(+) deficiency and points niacin to be an efficient NAD(+) booster for treating mitochondrial myopathy.