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Bounoua, H.

Publications and source records attributed to Bounoua, H..

2 recordsLinked to original sources

Pho92 direct interaction with Not1 recruits the CCR4-NOT complex to m6A containing mRNAs to modulate meiosis in S. cerevisiae

N6-methyladenosine (m6A) is the most abundant internal modification in eukaryotic mRNAs. In S. cerevisiae, m6A is exclusively deposited during meiosis, where it plays an essential role in meiotic progression. In this context, the absence of Pho92, the sole known m6A-binding protein in budding yeast, leads to the abnormal persistence of m6A-containing mRNAs, ultimately resulting in delayed meiosis. Here, we investigate how m6A recognition by Pho92 regulates gene expression. Using complementary in vivo and in vitro approaches, we identify direct interactions between Pho92 and Not1, the scaffold subunit of the CCR4-NOT deadenylase complex. Structural analyses reveal that a short evolutionarily conserved motif in Pho92 adopts an -helical conformation that docks onto specific regions of Not1. Functionally, these interactions are required for efficient meiotic progression. Altogether, our findings demonstrate that Pho92 couples m6A recognition to the main deadenylase to shape the meiotic transcriptome. More broadly, our work provides mechanistic insights into how epitranscriptomic signals interface with the core mRNA decay machinery to regulate gene expression during cellular differentiation.

molecular biology↗

The LH-DH module of the bacterial replicative helicases is the common binding site for DciA and other helicase loaders

During the initiation step of bacterial genome replication, replicative helicases depend on specialized proteins for their loading onto oriC. DnaC and DnaI were the first loaders characterized. However, most bacteria do not contain any of these genes, which are domesticated phage elements that replaced the ancestral and unrelated loader gene dciA several times during evolution. To understand how DciA assists the loading of DnaB, we determined the crystal structure of the complex from Vibrio cholerae, in which two VcDciAs interact with a dimer of VcDnaB, without changing its canonical structure. Our data showed that the VcDciA binding site on VcDnaB is the conserved module formed by the linker helix LH of one monomer and the determinant helix DH of the second one. Interestingly, DnaC from Escherichia coli also targets this module onto EcDnaB. Thanks to their common target site, we showed that VcDciA and EcDnaC could be functionally interchanged in vitro, despite sharing no structural similarities. This is a milestone in understanding the mechanism employed by phage helicase loaders to hijack bacterial replicative helicases during evolution.

molecular biology↗