LIM-domain-only (Lmo) proteins make up a family of transcription factors, of which all four members (Lmo1-4) have important roles in development, cell fate determination and a variety of cancers. In particular, Lmo1 and Lmo2 were discovered in association with chromosomal translations found in T cell leukaemia patients1, and are often found overexpressed in T-cell acute lymphoblastic leukaemia (T-ALL) patients, most often associated with bHLH oncogenes, including Tal12. 

The LIM domains of these Lmo proteins are zinc fingers that are only known to mediate protein protein interactions. These transcriptional regulators, therefore, must associate with transcription factors to form a complex which binds DNA. It is thought that the tightly regulated balance between Lmo proteins and these binding partners during development is important in their normal roles, and that a disturbance to this balance may trigger oncogenesis. 3,4

Lmo proteins tend to aggregate and be insoluble, but are stabilised by forming fusion constructs in which the Lmo proteins are tethered to a native binding partner, the LID (LIM interacting domain) of Ldb1. I have successfully designed, produced and characterised tethered Lmo-LID complexes of all four Lmo proteins. The folded state, secondary structure content, molecular weight and monodispersity were assessed by circular diachorism (CD), 1D NMR, and multi angle laser light scattering (MALLS) experiments. Higher order complex formation was assessed using electrophoretic mobility shift assays (EMSAs) and shows that LMO1–3 (but not LMO4) can interact with the bHLH protein Tal1.These new recombinant proteins will allow us to undertake structural and biochemical in vitro analysis and gain a better understanding of the critical balance of Lmo oncogenes and their binding partners.