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Structural basis for tunable affinity and specificity of LxCxE-dependent protein interactions with the retinoblastoma

Sivasankar Putta1, Lucia Alvarez2, Stephan Lüdtke3

  • 1Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.

Structure (London, England : 1993)
|June 18, 2022
PubMed

Insights

Retinoblastoma (Rb) proteins bind partners using a pocket domain. This study reveals how Rb proteins bind transcriptional co-repressors, explaining varying affinities and specificities for cancer-related interactions.

Area of Science:

  • Molecular biology
  • Structural biology
  • Cancer research

Background:

  • Retinoblastoma (Rb) proteins and homologs (p107, p130) regulate gene expression and cell cycle.
  • These proteins are frequently inactivated in various cancers.
  • Rb proteins bind the LxCxE motif in partner proteins to co-regulate transcription.

Purpose of the Study:

  • To elucidate the binding mechanism of the p107 pocket domain with LxCxE motifs from co-repressors.
  • To explain differential binding affinities between cellular proteins and viral proteins (HPV E7).
  • To identify structural determinants of Rb and p107 affinity and specificity for LxCxE sequences.

Main Methods:

  • X-ray crystallography to determine complex structures.
  • Co-immunoprecipitation assays for binding data.
  • Site-directed mutagenesis to probe protein-protein interactions.

Main Results:

  • Crystal structures of the p107 pocket domain bound to LxCxE peptides from HDAC1, ARID4A, and EID1 were determined.
  • Differences in binding affinity were explained by structural variations in LxCxE motifs and pocket domains.
  • The study provides insights into why viral LxCxE motifs bind Rb proteins with higher affinity than cellular partners.

Conclusions:

  • Rb protein family members exhibit specific binding preferences for LxCxE motifs.
  • Structural insights explain varying affinities, crucial for understanding transcriptional regulation in normal and cancer cells.
  • This research advances knowledge of protein-protein interactions involving Rb family proteins and their role in gene regulation.
Keywords:
Rb proteincell-cycle controlgene regulationp107 proteinprotein-protein interactionsshort linear motiftumor suppressorviral oncogene

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