The mechanism and consequences of loss of TAL1 in SIL-TAL leukaemia

We will consider applications from prospective students with:
a good biomedical degree.
good command of the English language as outlined in the postgraduate prospectus.
a source of funding to cover tuition fees and bench fees.

T-cell acute lymphoblastic leukaemia (T-ALL) is caused by abnormal T-cell development and often involves the aberrant expression of key transcription factors. In 20-25% of T-ALL, a ~90kb micro deletion on chromosome 1p32 results in the fusion of the SIL gene to the TAL1 gene, bringing the TAL1 gene under control of the transcriptional regulation of the SIL promoter. SIL is important for cell division with ubiquitous expression in all dividing cells, whereas TAL1 is an essential transcription factor regulating haematopoietic lineage specification and differentiation. The SIL-TAL fusion causes continuous TAL1 expression and thereby abnormal T-cell development. SIL-TAL patients are generally characterised by having high lymphoblast counts, high early mortality and a shorter relapse free and overall survival.
Based on gene expression microarrays of T-ALL patient samples, SIL-TAL belongs to a group of translocations that include chromosomal rearrangements of LMO1, LMO2 and LYL1. Interestingly the proteins encoded by these genes are part of the TAL1 transcriptional complex or homologous complexes. Whilst the LMO1/2 and LYL1 translocations mainly cause a block in T-cell development before the CD4/CD8 double positive stage, SIL-TAL is more variable and found in both T-ALL with immature T blasts, as well as in T-ALL with a more mature phenotype. One explanation for this may be found in an observation made by us and others. In SIL-TAL cell line models, as well as in patient samples, a significant proportion of the T-ALL where the SIL-TAL oncogene mRNA is expressed at high levels, shows TAL1 protein to be present at a very low or undetectable level. The loss of this oncogenic transcription factor is likely to be through proteasomal degradation. The molecular mechanism leading to TAL1 loss and its consequences in SIL-TAL T-ALL have not been addressed.
In order to investigate this we will examine several cell lines and use human CD34+ progenitors for overexpression studies of TAL1 isoforms and mutants, using doxycycline-inducible Lentiviral vectors. We will investigate the binding characteristics of TAL1 and other transcription factor complex members by ChIP-seq and the consequences this has on gene expression by RNA-seq. Finally, we will confirm the data from these experiments in patient samples.
Key experimental skills involved:
This project uses human cell lines and primary cells, as a source of material. Techniques used within this project include flow cytometry and magnetic or fluorescence activated cell sorting, protein pull-down assays followed by Western blotting and/or mass spectrometry, cloning of Lentiviral constructs, genome wide ChIP-seq and RNA-seq.