驱动蛋白Kin11调控嗜热四膜虫生殖系小核的减数分裂

驱动蛋白(kinesin)是分子马达蛋白质超家族成员,主要参与囊泡与细胞器的运输、纺锤体组装、有丝分裂和减数分裂等过程。在减数分裂期,不同驱动蛋白发挥功能的调控机制并不十分清楚。嗜热四膜虫(Tetrahymena thermophila)中含有14个驱动蛋白家族成员。其中,kinesin-6家族的唯一成员Kin11(TTHERM_00637750),在营养生长期低表达,饥饿期不表达,有性生殖期表达上调。Kin11编码1608个氨基酸,包含1个N端保守的马达蛋白结构域,C端卷曲螺旋(coiled-coil)结构域,并在N端和C端分别含有核定位信号NLS1和NLS2。Kin11在营养生长期和有性生殖期,定位在有丝分裂和减数分裂的小核和纺锤体上,并在有性生殖后期alignment阶段定位于小核上。Kin11与微管蛋白共定位于有丝分裂和减数分裂的纺锤体上。将Kin11的N端含有NLS1的1~400位氨基酸序列截短后,截断突变体定位在有性生殖减数分裂期的小核和纺锤体上。而将其C端含有NLS2的1008~1608位氨基酸残基截短后,截断突变体只能定位在有丝分裂和减数分裂后期的小核及有丝分裂的纺锤体上。敲除KIN11导致减数分裂过程中的纺锤体结构发生异常变化,小核染色体不均等分离与丢失,有性生殖发育停滞。结果表明,嗜热四膜虫驱动蛋白Kin11通过影响纺锤体结构,参与调控四膜虫生殖系小核在减数分裂过程中的正常分离。

Kinesin-11 Regulates Germline Micronucleus Meiosis in Tetrahymena thermophila

Kinesins are members of the motor protein superfamily.Most of kinesins move on microtubules and are involve in transport of vesicles and organelles,spindle assembly,and the process of mitosis and meiosis.The functions of different kinesins are indistinct during meiosis.Among the 14 kinesin family members identified in Tetrahymena thermophila,Kin11 was the sole member of the kinesin-6 family.The expression level of KIN11 is low at the vegetative growth stage,none during starvation,and high during early sexual reproduction.The KIN11 gene encoded a protein of 1608 amino acids that contained a conserved N-terminal motor domain and C-terminal coiled-coil domain.Immunofluorescence staining showed that Kin11 localized on the micronuclei(MICs)and the spindle during meiosis and mitosis progress of T.thermophila.Kin11 colocalized withα-tubulin on the spindle.The truncated kin11TrN 1-400 localized in the meiotic MICs and spindle,while the truncated kin11TrC 1008-1608 localized on the mitotic MICs and the spindle.Deletion of KIN11 leads to micronuclear chromosome abnormal segregation and loss during meiosis.Furthermore,the gametic nuclei failed to select and arrested sexual development.These results indicate that kin11 regulates micronucleus separation by affecting the spindle structure during meiosis in Tetrahymena thermophila.