ABSTRACT
Translocation t(3;22)(q27;q11) has recently been recognized as a recurrent abnormality in non-Hodgkin's malignant lymphoma (NHL). A new gene, LAZ3, has been shown to be involved in NHL with 3q27 rearrangement. Two patients with B-cell NHL were studied by chromosome painting and Southern blot analysis. Fluorescence in situ hybridization to metaphase chromosomes was shown to be an easy way to detect the chromosomal abnormality even in metaphase cells with poorly defined chromosomes. The gene LAZ3 was rearranged in one patient in the 'major translocation cluster region'. The comigration of rearranged LAZ3 and of IGL bands suggests that the translocation resulted in the juxtaposition of the two genes. This juxtaposition makes possible a potential deregulation of the LAZ3 gene expression, as previously shown for the MYC and BCL2 genes in Burkitt and follicular lymphoma translocations.
Subject(s)
Chromosomes, Human, Pair 22 , Chromosomes, Human, Pair 3 , Lymphoma, Non-Hodgkin/genetics , Translocation, Genetic , Aged , Blotting, Southern , Chromosome Mapping , Female , Gene Rearrangement , Genes, Neoplasm , Humans , In Situ Hybridization, Fluorescence , Lymphoma, B-Cell/genetics , Lymphoma, Follicular/genetics , Middle Aged , Zinc Fingers/geneticsABSTRACT
The LAZ3/BCL6 gene implicated in diffuse large cell lymphomas encodes a transcriptional repressor containing Krüppel-fike zinc fingers. It harbours at its N-terminus a conserved protein/protein interaction motif, the BTB/POZ domain, which is also an autonomous transcriptional repression domain. We demonstrate here using several GAL4-LAZ3/BCL6 chimeras that the BTB/POZ domain plays an important but not exclusive role as its deletion gives rise to a GAL4 chimera that mediates significant, albeit reduced, transcriptional repression. Moreover, the repressive effect mediated either by LAZ3/BCL6 or by the isolated domains occurs with unaltered efficiency even at long distance (1.6 Kbp), ruling out steric hindrance mechanisms. Finally, though the absence of a TATA box appears to weaken this activity, it is largely promoter independent. Taken together, our results demonstrate that multiple domains participate in the promoter and distance-independent LAZ3/BCL6-mediated transcriptional repression.