Anti-TLE2 monoclonal antibody Made to order

The punt related transcription factors RUNX (AML/CBF alpha/PEBP2 alpha) are key regulators of hematopoiesis and osteogenesis. Using co-transfection experiments with four natural promoters, including those of the osteocalcin (OC), multi drug resistance (MDR), Rous Sarcoma Virus long terminal repeat (LTR), and bone sialoprotein (BSP) genes, we show that each of these promoters responds differently to the forced expression of RUNX proteins. However, the three RUNX subtypes (i.e, AML1, AML2, and AML3) regulate each promoter in a similar manner. Although the OC promoter is activated in a C terminus dependent manner, the MDR, I,TR and BSP promoters are repressed by three distinct mechanisms, either independent of or involving the AML C terminus, or requiring only the conserved C-terminal pentapeptide VWRPY Using yeast two hybrid assays we find that the C terminus of AML1 interacts with a Groucho/TLE/R-esp repressor protein. Coexpression assays reveal that TLE proteins repress AML dependent activation of OC gene transcription. Western and northern blot analyses suggest that TLE expression is regulated reciprocally with the levels of OC gene expression during osteoblast differentiation. Digital immunofluorescence microscopy results show that TLE1 and TLE2 are both associated with the nuclear matrix, and that a significant subset of each colocalizes with AML transcription factors. This co-localization of TLE and AML proteins is lost upon removing the C terminus of AML family members. Our findings indicate that suppression of AML-dependent gene activation by TLE proteins involves functional interactions with the C terminus of AML at the nuclear matrix in situ, Our data are consistent with the concept that the C termini of AML proteins support activation or repression of cell-type specific genes depending on the regulatory organization of the target promoter and subnuclear localization.

The TLE genes constitute a family of important transcriptional co-repressors involved in many cellular processes. We found evidence of alternatively spliced mRNAs for human TLE1-4 containing premature stop codons, thus encoding putative shortened proteins. Microarray experiments and Real-time RT-PCR assays showed that alternatively spliced isoforms of TLE1, TLE2 and TLE3 were preferentially expressed in prostate in comparison to liver and kidney tissues. We identified by orientation-specific RT-PCR an antisense partially intronic non-coding RNA that overlaps a novel exon of the TLE3 gene, raising the possibility of regulation of alternative splicing by this non-coding transcript. The alternatively spliced isoform of TLE3 was up-regulated (6- to 17-fold) in prostate tumors in comparison to matched non-tumor adjacent tissue from 7 out of 11 (64%) patients and in four prostate tumor cell lines in comparison to a normal prostate cell line. These results demonstrate that different isoforms of TLE genes are commonly transcribed in human tissues and suggest that TLE3 could be involved in prostate cancer development. (C) 2007 Elsevier Inc. All rights reserved.