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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, RESULTS. Meshes: Adaptor Proteins, Signal Transducing, Amino Acid Motifs, Amino Acid Sequence, Animals, Apoptosis, Cell Line, Humans, Mice, Mutation, Proteasome Endopeptidase Complex, RNA Interference, RNA, Small Interfering, Staurosporine, Ubiquitin, Ubiquitination.
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Is hax-1 rapidly degraded by the proteasome dependent on its PEST sequence? Context: HS-1-associated protein X-1 (Hax-1), is a multifunctional protein that has sequence homology to Bcl-2 family members. HAX-1 knockout animals reveal that it plays an essential protective role in the central nervous system against various stresses. Homozygous mutations in the HAX-1 gene are associated with autosomal recessive forms of severe congenital neutropenia along with neurological symptoms. The protein level of Hax-1 has been shown to be regulated by cellular protease cleavage or by transcriptional suppression upon stimulation. Here, we report a novel post-translational mechanism for regulation of Hax-1 levels in mammalian cells. We identified that PEST sequence, a sequence rich in proline, glutamic acid, serine and threonine, is responsible for its poly-ubiquitination and rapid degradation. Hax-1 is conjugated by K48-linked ubiquitin chains and undergoes a fast turnover by the proteasome system. A deletion mutant of Hax-1 that lacks the PEST sequence is more resistant to the proteasomal degradation and exerts more protective effects against apoptotic stimuli than wild type Hax-1.
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Our data indicate that Hax-1 is a short-lived protein and that its PEST sequence dependent fast degradation by the proteasome may contribute to the rapid cellular responses upon different stimulations. Final Decision: yes