Institut Jean-Pierre Bourgin (IJPB), INRA, AgroParisTech, ERL-CNRS, Saclay Plant Sciences (SPS), Université Paris-Saclay, RD10, F-78026 Versailles, France.
UR1268 BIA, INRA Angers, Nantes Rue de la Geraudiere, 44316 Nantes Cedex 3, France.
Biochim Biophys Acta Gene Regul Mech. 2018 May;1861(5):443-450. doi: 10.1016/j.bbagrm.2018.03.005. Epub 2018 Mar 24.
The LAFL transcription factors LEC2, ABI3, FUS3 and LEC1 are master regulators of seed development. LEC2, ABI3 and FUS3 are closely related proteins that contain a B3-type DNA binding domain. We have previously shown that LEC1 (a NF-YB type protein) can increase LEC2 and ABI3 but not FUS3 activity. Interestingly, FUS3, LEC2 and ABI3 contain a B2 domain, the function of which remains elusive. We showed that LEC1 and LEC2 partially co-localised in the nucleus of developing embryos. By comparing protein sequences from various species, we identified within the B2 domains a set of highly conserved residues (i.e. TKxxARxxRxxAxxR). This domain directly interacts with LEC1 in yeast. Mutations of the conserved amino acids of the motif in the B2 domain abolished this interaction both in yeast and in moss protoplasts and did not alter the nuclear localisation of LEC2 in planta. Conversely, the mutations of key amino acids for the function of LEC1 in planta (D86K) prevented the interaction with LEC2. These results provide molecular evidences for the binding of LEC1 to B2-domain containing transcription factors, to form heteromers, involved in the control of gene expression.
LAFL 转录因子 LEC2、ABI3、FUS3 和 LEC1 是种子发育的主调控因子。LEC2、ABI3 和 FUS3 是密切相关的蛋白质，它们含有 B3 型 DNA 结合域。我们之前已经表明，LEC1（一种 NF-YB 型蛋白）可以增加 LEC2 和 ABI3 的活性，但不能增加 FUS3 的活性。有趣的是，FUS3、LEC2 和 ABI3 都含有 B2 结构域，但其功能尚不清楚。我们发现 LEC1 和 LEC2 部分在发育中的胚胎细胞核中共同定位于。通过比较来自不同物种的蛋白质序列，我们在 B2 结构域内鉴定出一组高度保守的残基（即 TKxxARxxRxxAxxR）。该结构域在酵母中直接与 LEC1 相互作用。在 B2 结构域中，该基序的保守氨基酸突变既破坏了酵母和藓原质体中的这种相互作用，也没有改变 LEC2 在植物体内的核定位。相反，在植物体内 LEC1 功能的关键氨基酸（D86K）突变阻止了与 LEC2 的相互作用。这些结果为 LEC1 与含有 B2 结构域的转录因子结合，形成异源二聚体，参与基因表达调控提供了分子证据。
