Yu, E. Y. | Search bioRxiv

bioRxiv2021

Reciprocal impacts of telomerase activity and tumor cell differentiation in neuroblastoma tumor biology

Telomere maintenance and tumor cell differentiation have been separately implicated in neuroblastoma malignancy. Their mechanistic connection is unclear. We analyzed neuroblastoma cell lines and morphologic subclones representing the adrenergic (ADRN) and mesenchymal (MES) differentiation states and uncovered sharp differences in their telomere protein and telomerase activity levels. Pharmacologic conversion of ADRN into MES cells elicited consistent and robust changes in the expression of telomere-related proteins. Conversely, stringent down-regulation of telomerase activity triggers the differentiation of ADRN into MES cells, which was reversible upon telomerase upregulation. Interestingly, the MES differentiation state is associated with elevated levels of innate immunity factors, including key components of the DNA-sensing pathway. Accordingly, MES but not ADRN cells can mount a robust response to viral infections in vitro. A gene expression signature based on telomere and cell lineage-related factors can cluster neuroblastoma tumor samples into predominantly ADRN or MES-like groups, with distinct clinical outcomes. Our findings establish a novel mechanistic connection between telomere and differentiation and suggest that manipulating telomeres may suppress malignancy not only by limiting the tumor growth potential but also by inducing tumor cell differentiation and altering its immunogenicity.

cancer biology↗

bioRxiv2020

Structurally distinct duplex telomere repeat-binding proteins in Ustilago maydis execute specialized, non-overlapping functions in telomere recombination and telomere protection

Duplex telomere binding proteins exhibit considerable structural and functional diversity in different phyla. Herein we address the distinct properties and functions of two Myb-containing, duplex telomere repeat-binding factors in Ustilago maydis, a basidiomycete fungus that is evolutionarily distant from the standard budding and fission yeasts. The two telomere-binding proteins in U. maydis, named UmTrf1 and UmTrf2, have different domain organizations and belong to distinct protein families with different phylogenetic distributions. Despite these differences, they exhibit comparable affinities and similar sequence specificity for the canonical, 6-base-pair telomere repeats. Deletion of trf1 triggers preferential loss of long telomere tracts, suggesting a role for the encoded protein in promoting telomere replication. Trf1 loss also partially suppresses the ALT-like phenotypes of ku70-deficient mutants, suggesting a novel role for a telomere protein in stimulating ALT-related pathways. In keeping with these ideas, we found that purified Trf1 can modulate the helicase activity of Blm, a conserved telomere replication and recombination factor. In contrast, trf2 appears to be essential and transcriptional repression of this gene leads to severe growth defects and profound telomere aberrations that encompass telomere length heterogeneity, accumulation of extrachromosomal telomere repeats such as C-circles, and high levels of single-stranded telomere DNA. These observations support a critical role for UmTrf2 in telomere protection. Together, our findings point to a unique, unprecedented division of labor between the two major duplex telomere repeat-binding factors in Ustilago maydis. Comparative analysis of UmTrf1 homologs in different phyla reveals a high degree of functional diversity for this protein family, and provides a case study for how a sequence-specific DNA binding protein can acquire and lose functions at different chromosomal locations.

molecular biology↗