PAX5 is part of a functional transcription factor network targeted in lymphoid leukemia.

Kazuki Okuyama,Jacob Kuruvilla,Tobias Strid,Rajesh Somasundaram,Susana Cristobal,Thoas Fioretos,Jonas Ungerbäck,Shamit Soneji,Mahadesh Prasad,Emma Smith,Henrik Lilljebjörn,Mikael Sigvardsson,Stefan Lang

doi:10.1371/journal.pgen.1008280

Kazuki Okuyama, Jacob Kuruvilla + Show 11 more

Open Access

https://doi.org/10.1371/journal.pgen.1008280

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Journal: PLoS Genetics	Publication Date: Aug 5, 2019
Citations: 34	License type: CC BY 4.0

Affiliation: Linköping University, Lund University

Abstract

One of the most frequently mutated proteins in human B-lineage leukemia is the transcription factor PAX5. These mutations often result in partial rather than complete loss of function of the transcription factor. While the functional dose of PAX5 has a clear connection to human malignancy, there is limited evidence for that heterozygote loss of PAX5 have a dramatic effect on the development and function of B-cell progenitors. One possible explanation comes from the finding that PAX5 mutated B-ALL often display complex karyotypes and additional mutations. Thus, PAX5 might be one component of a larger transcription factor network targeted in B-ALL. To investigate the functional network associated with PAX5 we used BioID technology to isolate proteins associated with this transcription factor in the living cell. This identified 239 proteins out of which several could be found mutated in human B-ALL. Most prominently we identified the commonly mutated IKZF1 and RUNX1, involved in the formation of ETV6-AML1 fusion protein, among the interaction partners. ChIP- as well as PLAC-seq analysis supported the idea that these factors share a multitude of target genes in human B-ALL cells. Gene expression analysis of mouse models and primary human leukemia suggested that reduced function of PAX5 increased the ability of an oncogenic form of IKZF1 or ETV6-AML to modulate gene expression. Our data reveals that PAX5 belong to a regulatory network frequently targeted by multiple mutations in B-ALL shedding light on the molecular interplay in leukemia cells.

Highlights

It is becoming increasingly clear that transcription factors essential for normal B-cell development are frequently mutated in B-lineage Acute Lymphoblastic Leukemia (B-ALL) [1]
Using Chromatin Immuno-precipitation (ChIP)-seq, proximity ligation assisted ChIP-seq (PLAC-seq) [15] and RNA-seq analysis we confirmed that PAX5, RUNX1 and IKZF1 share a large number of target genes and that a dominant negative form of IKZF1 or the ETV6-RUNX1 fusion protein acted collaboratively with heterozygote deletion of Pax5 to modulate gene expression
The fusion proteins were ectopically expressed in a mouse Abelson virus transformed Pre-B cell line (230–238), after which biotinylated proteins were purified on streptavidin beads

Summary

Introduction

It is becoming increasingly clear that transcription factors essential for normal B-cell development are frequently mutated in B-lineage Acute Lymphoblastic Leukemia (B-ALL) [1]. Using Chromatin Immuno-precipitation (ChIP)-seq, proximity ligation assisted ChIP-seq (PLAC-seq) [15] and RNA-seq analysis we confirmed that PAX5, RUNX1 and IKZF1 share a large number of target genes and that a dominant negative form of IKZF1 or the ETV6-RUNX1 fusion protein acted collaboratively with heterozygote deletion of Pax to modulate gene expression. This suggest that the transformation process in B-ALL involve multiple mutations of genes being part of a regulatory network possibly causing an exacerbated effect on the transcriptional programming in the B-cell progenitor

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Discussion

Conclusion