Bmi1 Confers Resistance to Oxidative Stress on Hematopoietic Stem Cells

The polycomb-group (PcG) proteins function as general regulators of stem cells. We previously reported that retrovirus-mediated overexpression of Bmi1, a gene encoding a core component of polycomb repressive complex (PRC) 1, maintained self-renewing hematopoietic stem cells (HSCs) during long-term culture. However, the effects of overexpression of Bmi1 on HSCs in vivo remained to be precisely addressed.In this study, we generated a mouse line where Bmi1 can be conditionally overexpressed under the control of the endogenous Rosa26 promoter in a hematopoietic cell-specific fashion (Tie2-Cre;R26Stop(FL)Bmi1). Although overexpression of Bmi1 did not significantly affect steady state hematopoiesis, it promoted expansion of functional HSCs during ex vivo culture and efficiently protected HSCs against loss of self-renewal capacity during serial transplantation. Overexpression of Bmi1 had no effect on DNA damage response triggered by ionizing radiation. In contrast, Tie2-Cre;R26Stop(FL)Bmi1 HSCs under oxidative stress maintained a multipotent state and generally tolerated oxidative stress better than the control. Unexpectedly, overexpression of Bmi1 had no impact on the level of intracellular reactive oxygen species (ROS).Our findings demonstrate that overexpression of Bmi1 confers resistance to stresses, particularly oxidative stress, onto HSCs. This thereby enhances their regenerative capacity and suggests that Bmi1 is located downstream of ROS signaling and negatively regulated by it

Hypervalent Iodine(III)-Mediated Oxidative Decarboxylation of β,γ-Unsaturated Carboxylic Acids

A novel oxidative decarboxylation of β,γ-unsaturated carboxylic acids mediated by hypervalent iodine­(III) reagents is described. The decarboxylative C–O bond forming reaction proceeded in the presence of PhI­(OAc)₂ to give the corresponding allylic acetates. In addition, decarboxylative C–N bond formation was achieved by utilizing hypervalent iodine­(III) reagents containing an I–N bond. Mechanistic studies suggest the unique reactivity of hypervalent iodine reagents in this ionic oxidative decarboxylation

Hypervalent Iodine(III)-Mediated Oxidative Decarboxylation of β,γ-Unsaturated Carboxylic Acids

A novel oxidative decarboxylation of β,γ-unsaturated carboxylic acids mediated by hypervalent iodine­(III) reagents is described. The decarboxylative C–O bond forming reaction proceeded in the presence of PhI­(OAc)₂ to give the corresponding allylic acetates. In addition, decarboxylative C–N bond formation was achieved by utilizing hypervalent iodine­(III) reagents containing an I–N bond. Mechanistic studies suggest the unique reactivity of hypervalent iodine reagents in this ionic oxidative decarboxylation

Comparisons of Early Growth between Seedlings and Sprouts, and Relationship between Original Tree Size and Vigor of Sprouts of Pusania edulis

Early growth characteristics were compared between seedlings and sprouts of Pasania edulis developed after clear cutting of the forest stand, and a relationship between the original plant size before cutting and the vigor of sprouts was also investigated. The early growth of sprouts during the first growing season were far greater than those of seedlings on both individual and unit area basis. The sprouts showed unique growth characteristics. They developed non-photosynthetic parts earlier than photosynthetic parts to expand foliage at more advantageous position which might be supported by the abundant reserved substances and large water and mineral absorbing capacity of the original root system compared with those of seedlings. The vigor of sprouts was closely related to the original plant size used in this study as an index of the amount of reserved substances. However, even if the number of sprouts per unit reserved substances decreased, use efficiency of reserved substance did not increase. This result may suggest the possibility that all of the reserved substances are not utilized for regrowth by sprouts

Comparisons of Early Growth between Seedlings and Sprouts, and Relationship between Original Tree Size and Vigor of Sprouts of Pusania edulis

Early growth characteristics were compared between seedlings and sprouts of Pasania edulis developed after clear cutting of the forest stand, and a relationship between the original plant size before cutting and the vigor of sprouts was also investigated. The early growth of sprouts during the first growing season were far greater than those of seedlings on both individual and unit area basis. The sprouts showed unique growth characteristics. They developed non-photosynthetic parts earlier than photosynthetic parts to expand foliage at more advantageous position which might be supported by the abundant reserved substances and large water and mineral absorbing capacity of the original root system compared with those of seedlings. The vigor of sprouts was closely related to the original plant size used in this study as an index of the amount of reserved substances. However, even if the number of sprouts per unit reserved substances decreased, use efficiency of reserved substance did not increase. This result may suggest the possibility that all of the reserved substances are not utilized for regrowth by sprouts