Protein post-translational modification by lysine succinylation:Biochemistry,biological implications,and therapeutic opportunities

Lysine succinylation(Ksuc)is a novel protein post-translational modification(PTM)wherein a succinyl group modifies a lysine residue.Ksuc leads to significant chemical and struc-tural changes to the modified protein.Recent studies have shown that Ksuc might play an important role in organism physiology and some pathophysiological processes,such as tumor-igenesis and metabolic diseases.To provide an understanding of the molecular mechanism and functions of Ksuc in different organisms,we reviewed the current literature about Ksuc,mainly summarizing the research advances in eukaryotes and prokaryotes based on both traditional study methods and site prediction tools.We also discussed inhibitors or activators associated with Ksuc that may contribute to proteomic studies and could be useful in future clinical prac-tice.A deeper understanding of Ksuc may shed new light on life science at the protein level and could lead to novel therapeutic strategies for various diseases.

HBB-deficient Macaca fascicularis monkey presents with human β-thalassemia

Dear Editor,β-Thalassemia is a common severe genetic disease caused by mutations in HBB and affects approximately 1.5% of the global population (Origa, 2017). In southern China, the carrier rate of β-thalassemia is as high as 6.43%, creating a high socio-economic burden (Xiong et al., 2010). In adult humans, there are three types of hemoglobin: HbA1 (~97%), HbA2 (~2%) and HbF (~1%). HbA1 (α2β2) is composed of two a-globin and two β-globi n sub units en coded by HBA and HBB, respectively;HbF (α2β2)is made up of two α-globin subunits and two β-globin sub units en coded by HBG. Mutations in the coding region or regulatory region of HBB are involved in β-thalassemia pathogenesis. Except for some rare dominant mutations, most HBB mutations are recessive (Origa, 2017). Depending on the mutation type, the β-globin level will either be reduced or completely depleted, resulting in α-globin accumulation and precipitation. These α-globin precipitates lead to red blood cell death, resulting in anemia and tissue damage, and even death in thalassemia major patients. Blood transfusions can help slow disease progression but lead to iron overload, ultimately resulting in iron toxicity. Bone marrow transfer is the only cure in the clinic and is available only to a small percentage of patients with human leukocyte antigervmatched donors. Recently, gene therapy and gene editing therapy have shown great promise in curing β-thalassemia (Glaser et al., 2015;Thompson et al., 2018). However, no appropriate animal models are available for evaluating the safety and efficacy of such advanced therapeutic strategies in vivo.β-thalassemia mice are the sole animal model available for research. However, substantial differences have been reported between the types and expressi on patter ns of human and mouse globins (McColl and Vadolas, 2016). Moreover, mice contain no fetal globin gene equivalent, and homozygous mutations of HBB in mouse for early models of β-thalassemia major or Cooley anemia are all embryonic lethal (Huo et al., 2009). Recently, significant phenotype and physiology differences have been reported between SIRT6- null mice and the non-human primate model (Zhang et al., 2018). Thus, an appropriate non-human primate model is needed for human β-thalassemia studies and treatments.