The 8 kD product of the putative oncogene MTCP-1 is a mitochondrial protein.

An unusually small (8 kD) protein (p8MTCP-1) is coded by the putative oncogene MTCP-1 (also called c6.1B), involved in the translocation t(X;14)(q28;q11) associated with some mature T-cell proliferations. Here, we show by subcellular fractionation and by confocal microscopy that this protein is located in the mitochondria. This localization orientates toward a role of p8MTCP-1 in the mitochondrial metabolism which may be relevant for the oncogenic process.

Lymphoid specificity of a copy number-related expression of the H2-Kb transgene.

Transcriptional regulation of the MHC class I genes leading to their developmental and tissue specific expression is still poorly understood in spite of the recovery of a large variety of cis-controlling sequences and trans-acting factors pertaining to the 5' enhancer and the downstream regulatory element. Here we produced a series transgenic lines of mice with a genomic subclone of the H2-Kb gene consisting of 367 bp of the 5' upstream region, the coding region and 1.5 kb of the 3' downstream region and carrying all hitherto known regulatory sequences. The comparison of nine transgenic lines carrying the same H2-Kb transgene made it possible to ask whether the cis-information present in the transgene was sufficient for the tissue- and developmental-specific expression and its copy number dependence. We found the proper developmental onset of expression of the transgene at day 13 p.c. and correct tissue specific mRNA levels in adult mice. While in lymphoid tissues and in lung the number of transgene copies still correlated with RNA levels, the copy number dependence was completely lost in liver, kidney and embryonic tissues. Comparison with previously published H2-Kb transgenes indicates that the H2-Kb locus-controlling region is composed of more than one element.

The absence of human beta 2-microglobulin increases the occurrence of ankylosing enthesopathy in HLA-B27 transgenic mice.

HLA-B27 transgenic mice develop a spontaneous ankylosing enthesopathy (ANKENT). We have investigated the occurrence of ANKENT in transgenic mice carrying transgenes for human beta 2-microglobulin (M TGM), HLA-B27-heavy chain (27 TGM), or both (27M TGM). An unexpected finding was the increase in ANKENT occurrence among the HLA-B27 transgenic mice lacking the human beta 2-microglobulin transgene (27 TGM): 33% of such mice were found to develop ANKENT, whereas 19% of 27M mice were diseased. In addition, the expression of HLA-B27 molecules in individual 27 TGM was highly variable, ranging from no expression to a level similar to that observed in 27M TGM. Our results confirm that in mice the HLA-B27 transgene is a relative risk factor for ANKENT. The increase of ANKENT occurrence is HLA-B27 transgenics in the absence of human beta 2-microglobulin suggests a possible role for impaired cell surface expression of HLA-B27. The absence of human beta 2-microglobulin might entail an accumulation of unassembled HLA-B27 heavy chains. Exposure of these mice to an environmental trigger could then lead to an inappropriate immune response which might result in disease development.