In <i>S</i>. <i>pombe</i>, Gemin2 overexpression affects cell viability through retention of Sm proteins in the cytoplasm.

<p>(<b>A</b>) Wild-type or <i>tdSmn</i> cells were transformed with a plasmid carrying the <i>S</i>. <i>pombe Smn</i> gene, a plasmid carrying the <i>S</i>. <i>pombe Gemin2</i> gene or with the empty pREP3∆ vector. Cultures of comparable density were then serially diluted, spotted on EMM2-Leu plates in the presence (expression is repressed) or absence (expression is induced) of Thiamine and incubated at 25°C for 5 days to test for their growth ability. In a wild-type or <i>tdSmn</i> background, growth defects are induced by upregulation of SpGem2 but not SpSMN. (<b>B</b>) Wild-type or <i>tdSmn</i> cells were transformed with a plasmid carrying GFP.SmB in combination with the plasmids indicated on the right. Cultures of comparable density were then serially diluted, spotted on EMM2-Leu-Ura- plates in the presence (expression is repressed) or absence (expression is induced) of Thiamine and incubated at 25°C for 5 days to examine their growth ability. The growth defect of either wild-type or <i>tdSMN</i> cells overexpressing Gemin2 is not complemented by an increase in the levels of SmB. <i>tdSMN</i> cells overexpressing both SmB and SpSMN, as expected, grew better than the control. However, the growth of wild-type cells with the same genetic modification was marginally inferior. (<b>C</b>) In GFP.SmB-expressing wild-type cells, SmB is predominantly localised to the nucleus. On upregulation of Gemin2, SmB accumulates in the cytoplasm and cells exhibit an elongated phenotype.