HAUS4

HAUS4 is a subunit of the Augmin/HAUS complex that promotes microtubule nucleation along the mitotic spindle and maintains centrosome integrity during mitosis (PMID:28596487). Combined depletion of HAUS4 with HAUS5 causes centrosome fragmentation and lethality in neural progenitor cells, indicating that HAUS4 acts redundantly within the complex to support spindle and centrosome organization (PMID:28596487). Loss of HAUS4 also reduces proliferation and activates the senescence markers p16 and p21, placing it among genes required to prevent senescence entry (PMID:32264951). Beyond these complex- and phenotype-level observations, no direct biochemical mechanism for HAUS4 itself has been characterized in the available corpus.

1. 2017 Medium

   Established HAUS4 as a functional, partially redundant member of the Augmin/HAUS complex needed for spindle microtubule nucleation and centrosome integrity, addressing whether HAUS4 contributes to mitotic spindle assembly.

   Evidence siRNA double knockdown of HAUS5 with HAUS4 in neural progenitor cells, scoring centrosome fragmentation and viability

   PMID:28596487

   Open questions at the time

   • HAUS4 role inferred from double-knockdown epistasis rather than direct mechanistic study of HAUS4 alone
   • No biochemical assay of HAUS4's contribution to microtubule nucleation
   • Single-lab, single cell-type observation
2. 2020 Medium

   Linked HAUS4 loss-of-function to senescence entry, addressing the cellular consequence of HAUS4 depletion beyond mitotic defects.

   Evidence siRNA knockdown with readouts of cell number, p16/p21 activation, and senescence morphology

   PMID:32264951

   Open questions at the time

   • Part of a large screen with no molecular mechanism defined downstream of HAUS4
   • Causal link between mitotic/centrosome defects and senescence not directly established

• The direct molecular activity of HAUS4 within the Augmin/HAUS complex and how its loss mechanistically triggers senescence remain undefined.
• No structural or biochemical characterization of HAUS4's role in microtubule nucleation
• No mapped interaction interfaces within the HAUS complex
• Mechanism connecting centrosome fragmentation to p16/p21 activation unresolved