驱动蛋白Kin11调控嗜热四膜虫生殖系小核的减数分裂

Kinesin is a member of the molecular motor protein superfamily and is mainly involved in processes such as the transport of vesicles and organelles, spindle assembly, mitosis and meiosis. During meiosis, the regulatory mechanisms by which different kinesins function are not very clear. Tetrahymena thermophila contains 14 members of the kinesin family. Among them, Kin11 (TTHERM_00637750), the only member of the kinesin - 6 family, is lowly expressed during the vegetative growth phase, not expressed during the starvation phase, and its expression is upregulated during the sexual reproduction phase. Kin11 encodes 1,608 amino acids, contains a conserved motor protein domain at the N - terminus, a coiled - coil domain at the C - terminus, and contains nuclear localization signals NLS1 and NLS2 at the N - terminus and C - terminus respectively. During the vegetative growth phase and the sexual reproduction phase, Kin11 is localized on the micronucleus and spindle of mitosis and meiosis, and is localized on the micronucleus during the alignment stage in the later period of sexual reproduction. Kin11 is co - localized with tubulin on the spindle of mitosis and meiosis. After truncating the amino acid sequence from positions 1 to 400 at the N - terminus of Kin11 containing NLS1, the truncated mutant is localized on the micronucleus and spindle during meiosis of sexual reproduction. While after truncating the amino acid residues from positions 1,008 to 1,608 at the C - terminus containing NLS2, the truncated mutant can only be localized on the micronucleus in the later period of mitosis and meiosis and on the spindle of mitosis. The knockout of KIN11 leads to abnormal changes in the spindle structure during meiosis, unequal separation and loss of micronuclear chromosomes, and stagnation of sexual reproductive development. The results indicate that the kinesin Kin11 of Tetrahymena thermophila participates in regulating the normal separation of the germline micronucleus of Tetrahymena during meiosis by affecting the spindle structure.

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1 608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1 008~1 608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。