Cherel I, Thuriaux P
Service de Biochimie & Génétique Moléculaire, CEA (Saclay), Gif sur Yvette, France.
Yeast. 1995 Mar;11(3):261-70. doi: 10.1002/yea.320110308.
FHL1 encodes a polypeptide closely related to the fork head protein family of transcriptional activators. Deleting this gene leads to a slow-growth phenotype with impaired rRNA maturation. IFH1 (located on chromosome IV) was isolated as a dosage-dependent suppressor partially correcting the growth defect of the fhl1 deletion. It codes for a highly hydrophilic protein with a predicted molecular weight of 122 kDa and a pI of 4.8, that is very rich in charged residues (mostly acidic) but otherwise unrelated to any known protein. Carboxy-terminal deletions removing the last third of the protein lead to a leaky growth phenotype with impaired rRNA maturation, as in the case of the fhl1 deletion. A full deletion of IFH1 is lethal, but growth was restored in a strain deleted for both IFH1 and FHL1. Thus, Ifh1p is essential for growth, but only in the presence of a functional Fhp1p protein. Conversely, its overexpression by increased gene dosage partially compensates for the genetic inactivation of Fhl1p. These data suggest a direct interaction between the Fhl1p and Ifh1p proteins, and are consistent with a model where Fhl1p is converted from a transcriptional repressor to an activator on binding of Ifh1p.
FHL1编码一种与转录激活因子的叉头蛋白家族密切相关的多肽。删除该基因会导致生长缓慢的表型，同时rRNA成熟受损。IFH1（位于第四条染色体上）作为一种剂量依赖性抑制因子被分离出来，它能部分纠正fhl1缺失导致的生长缺陷。它编码一种高度亲水的蛋白质，预测分子量为122 kDa，pI为4.8，该蛋白质富含带电荷的残基（大多为酸性），但与任何已知蛋白质无关。去除蛋白质最后三分之一的羧基末端缺失会导致生长渗漏表型，rRNA成熟受损，就像fhl1缺失的情况一样。完全删除IFH1是致死的，但在同时缺失IFH1和FHL1的菌株中生长得以恢复。因此，Ifh1p对生长至关重要，但仅在存在功能性Fhp1p蛋白的情况下。相反，通过增加基因剂量对其进行过表达可部分补偿Fhl1p的基因失活。这些数据表明Fhl1p和Ifh1p蛋白之间存在直接相互作用，并且与一个模型一致，即Fhl1p在与Ifh1p结合时从转录抑制因子转变为激活因子。
