Structure of human BCCIP and implications for binding and modification of partner proteins

Inhibition of FAM46/TENT5 activity by BCCIPα adopting a unique fold

The FAM46 (also known as TENT5) proteins are noncanonical poly(A) polymerases (PAPs) implicated in regulating RNA stability. The regulatory mechanisms of FAM46 are poorly understood. Here, we report that the nuclear protein BCCIPα, but not the alternatively spliced isoform BCCIPβ, binds FAM46 and inhibits their PAP activity. Unexpectedly, our structures of the FAM46A/BCCIPα and FAM46C/BCCIPα complexes show that, despite sharing most of the sequence and differing only at the C-terminal portion, BCCIPα adopts a unique structure completely different from BCCIPβ. The distinct C-terminal segment of BCCIPα supports the adoption of the unique fold but does not directly interact with FAM46. The β sheets in BCCIPα and FAM46 pack side by side to form an extended β sheet. A helix-loop-helix segment in BCCIPα inserts into the active site cleft of FAM46, thereby inhibiting the PAP activity. Our results together show that the unique fold of BCCIPα underlies its interaction with and functional regulation of FAM46.

Identifying NFKB1, STAT3, and CDKN1A as Baicalein's Potential Hub Targets in Parkinson's Disease-related α-synuclein-mediated Pathways by Integrated Bioinformatics Strategies

BACKGROUND

The overexpression, accumulation, and cell-to-cell transmission of α-synuclein leads to the deterioration of Parkinson's disease (PD). Previous studies suggest that Baicalein (BAI) can bind to α-synuclein and inhibit α-synuclein aggregation and secretion. However, it is still unclear whether BAI can intervene with the pathogenic molecules in α-synuclein-mediated PD pathways beyond directly targeting α-synuclein per se.

METHODS

This study aimed to systematically investigate BAI's potential targets in PD-related A53T mutant α-synuclein-mediated pathways by integrating data mining, network pharmacological analysis, and molecular docking simulation techniques.

RESULTS

The results suggest that BAI may target genes that are dysregulated in synaptic transmission, vesicle trafficking, gene transcription, protein binding, extracellular matrix formation, and kinase activity in α-synucleinmediated pathways. NFKB1, STAT3, and CDKN1A are BAI's potential hub targets in these pathways.

CONCLUSION

Our findings highlight BAI's potentiality to modulate α-synuclein-mediated pathways beyond directly targeting α-synuclein per se.

Structure of human BCCIP and implications for binding and modification of partner proteins

BCCIP was isolated based on its interactions with tumor suppressors BRCA2 and p21. Knockdown or knockout of BCCIP causes embryonic lethality in mice. BCCIP deficient cells exhibit impaired cell proliferation and chromosome instability. BCCIP also plays a key role in biogenesis of ribosome 60S subunits. BCCIP is conserved from yeast to humans, but it has no discernible sequence similarity to proteins of known structures. Here we report two crystal structures of an N-terminal truncated human BCCIPβ, consisting of residues 61-314. Structurally BCCIP is similar to GCN5-related acetyltransferases (GNATs) but contains different sequence motifs. Moreover, both acetyl-CoA and substrate-binding grooves are altered in BCCIP. A large 19-residue flap over the putative CoA binding site adopts either an open or closed conformation in BCCIP. The substrate binding groove is significantly reduced in size and is positively charged despite the acidic isoelectric point of BCCIP. BCCIP has potential binding sites for partner proteins and may have enzymatic activity.