BCL-XL regulates the timing of mitotic apoptosis independently of BCL2 and MCL1 compensation.

Mitotic catastrophe induced by prolonged mitotic arrest is a major anticancer strategy. Although antiapoptotic BCL2-like proteins, including BCL-XL, are known to regulate apoptosis during mitotic arrest, adaptive changes in their expression can complicate loss-of-function studies. Our studies revealed compensatory alterations in the expression of BCL2 and MCL1 when BCL-XL is either downregulated or overexpressed. To circumvent their reciprocal regulation, we utilized a degron-mediated system to acutely silence BCL-XL just before mitosis. Our results show that in epithelial cell lines including HeLa and RPE1, BCL-XL and BCL2 acted collaboratively to suppress apoptosis during both unperturbed cell cycle and mitotic arrest. By tagging BCL-XL and BCL2 with a common epitope, we estimated that BCL-XL was less abundant than BCL2 in the cell. Nonetheless, BCL-XL played a more prominent antiapoptotic function than BCL2 during interphase and mitotic arrest. Loss of BCL-XL led to mitotic cell death primarily through a BAX-dependent process. Furthermore, silencing of BCL-XL led to the stabilization of MCL1, which played a significant role in buffering apoptosis during mitotic arrest. Nevertheless, even in a MCL1-deficient background, depletion of BCL-XL accelerated mitotic apoptosis. These findings underscore the pivotal involvement of BCL-XL in controlling timely apoptosis during mitotic arrest, despite adaptive changes in the expression of other BCL2-like proteins.

[Polymorphism of DXYS267 locus and application of its Y-specific single nucleotide substitutions].

OBJECTIVE: To investigate the polymorphism of DXYS267 locus in China Han population and find the application and characters of its Y-specific single nucleotide substitutions. METHODS: The locus was analyzed by PCR and PAGE in silver-staining. The Y-specific STR was amplified with newly designed primers according to the Y-specific single nucleotide substitutions. RESULTS: Six alleles were detected in Han population in Wuhan. Exact tests demonstrated that genotype frequencies did not deviate from Hardy-Weinberg equilibrium. Heterozygosity of DXYS267 was 0.6706, discrimination power (DP) was 0.8433, and the probability of paternity exclusion (PE) was 0.5957. The Y-specific STR of DXYS267 was successfully amplified with the new primer. The 4 alleles for Y-STR were detected with haplotype diversity (HD) 0.6372. CONCLUSION: The DXYS267 locus is appropriate for individual identification and paternity testing. The new primer is useful for individual and paternity testing involving brothers and mixed stains.