LMO4

LMO4 Full Name

LIM domain only 4

LMO4 Introduction

LMO4 encodes a cysteine-rich nuclear protein that contains two LIM domains but lacks a DNA-binding homeodomain, classifying it as a LIM-only factor that works as a scaffolding adapter rather than a direct DNA-binding transcription factor. The LIM domains mediate protein-protein interactions, allowing LMO4 to assemble multi-subunit complexes with partners such as the LIM-domain-binding proteins (LDB/CLIM), the corepressors CtIP and C-terminal binding protein, histone deacetylases, and the BRCA1 tumor suppressor. Its two LIM domains are zinc-binding modules that act as docking platforms, and their precise spacing is critical for assembling the higher-order complexes that dictate target-gene selection. Through these assemblies LMO4 modulates the activity of diverse signaling pathways, including transforming growth factor-beta/Smad and estrogen receptor-alpha networks. First identified through its recruitment by the deformed epidermal autoregulatory factor 1 transcription factor, LMO4 is expressed widely with particularly high levels in the developing and adult brain, where it contributes to neuronal connectivity and sensory organ formation.

Figure 1. LMO4/ldb1-LID protein constructs. (Source: Jeffries CM, et al. 2006)

In the mammary gland, LMO4 has emerged as a pivotal regulator of both normal morphogenesis and cancer. Transgenic overexpression in mice causes hyperplasia and tumor formation, and LMO4 is frequently up-regulated in human breast cancers, especially estrogen-receptor-negative subtypes. Mechanistically, LMO4 promotes epithelial cell proliferation and survival while repressing apoptosis, actions that can be reversed by dominant-negative constructs that block its transcriptional activity. It controls target genes such as bone morphogenetic protein 7 through an HDAC2-dependent mechanism, and it inhibits BRCA1-mediated transcription, hinting at how it may cooperate with breast tumor suppressors. LMO4 is also re-expressed during epithelial-to-mesenchymal transition in neural crest-derived tumors, reflecting its broader role as a plasticity factor. Loss-of-function studies in mice further reveal roles for LMO4 in cranial neural crest derivatives, indicating that its developmental footprint extends well beyond the mammary gland. Together these findings place LMO4 at the intersection of developmental patterning and oncogenesis, where it couples extracellular cues to gene-expression programs that favor cell growth and resistance to death.

Alternate Names for LMO4

LMO4; LIM domain only 4; LIM domain transcription factor LMO4; LMO-4; ethanol induced 4; breast tumor autoantigen; LIM domain only protein 4; Crp3; Etohi4; A730077C12Rik;

• 1. Jeffries CM, et al. Stabilization of a binary protein complex by intein-mediated cyclization. Protein Sci. 2006 Nov;15(11):2612-8.
  2. Tian Y, et al. Repression of Lim only protein 4-activated transcription inhibits proliferation and induces apoptosis of normal mammary epithelial cells and breast cancer cells. Clin Exp Metastasis. 2010 Oct;27(7):455-63.