PubMed · 6163261
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K O Vorlaender, B Schmolke. 1981-01-31. [Tumor diagnosis using immunologic methods].. https://pubmed.ncbi.nlm.nih.gov/6163261/
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The SUMO family in vertebrates includes at least three distinct proteins (SUMO-1, -2, and -3) that are added as post-translational modifications to target proteins. A considerable number of SUMO-1 target proteins have been identified, but little is known about SUMO-2. A stable HeLa cell line expressing His6-tagged SUMO-2 was established and used to label and purify novel endogenous SUMO-2 target proteins. Tagged forms of SUMO-2 were functional and localized predominantly in the nucleus. His6-tagged SUMO-2 conjugates were affinity-purified from nuclear fractions and identified by mass spectrometry. Eight novel potential SUMO-2 target proteins were identified by at least two peptides. Three of these proteins, SART1, heterogeneous nuclear ribonucleoprotein (RNP) M, and the U5 small nuclear RNP 200-kDa helicase, play a role in RNA metabolism. SART1 and heterogeneous nuclear RNP M were both shown to be genuine SUMO targets, confirming the validity of the approach.
Previous work has shown that melanoma cell lines express a distinct octamer binding protein. Given the role of octamer-binding proteins in cell differentiation and development, the role this factor is a key issue in understanding melanocyte differentiation and transformation. Using a proteolytic clipping assay, we show that the melanoma-specific octamer factor is Brn-2/N-Oct3, a POU domain protein previously known to be expressed in adult brain and in the developing nervous system. N-Oct3 mRNA was detected in a range of human melanoma cell lines and was around 10-fold elevated compared to normal human melanocytes while mRNA for Brn-2 was also detected in a mouse melanoblast cell line. Expression of Brn-2/N-Oct3, in melanoma cells in cotransfection assays activated the expression of the MHC class II DR alpha promoter but repressed the activity of the melanocyte-specific tyrosinase promoter. Repression correlated with Brn-2/N-Oct3 binding in a mutually exclusive fashion with basic-helix-loop-helix-leucine-zipper (bHLH-LZ) transcription factor USF in vitro and with Brn-2 expression preventing activation of the tyrosinase promoter by the bHLH-LZ factor Microphthalmia in vivo. The potential role of Brn-2/N-Oct3 in melanocyte differentiation and gene expression is discussed.
The MAGE genes encode certain tumor-associated antigens recognized by cytotoxic T lymphocytes. We investigated the expression of the MAGE-1, -2, -3, -4, -41, and -6 genes in 88 head-and-neck squamous-cell carcinomas (83 fresh tumor samples and 5 cell lines), using a reverse-transcription-polymerase-chain-reaction assay, followed by dot-blot hybridization with sequence-specific oligonucleotides and/or restriction enzyme-pattern analysis. The MAGE-1, -2, -3, -4, -41 and -6 genes were expressed at the mRNA level in 27, 34, 36, 22, 16 and 35, respectively, of 83 fresh tumor samples. At least one of these genes was expressed in 59 of the 83 samples. Neither non-tumor inflammatory cells nor normal tissues were positive for these genes. The MAGE-1 gene was expressed relatively frequently in SCC of the oropharynx, hypopharynx and maxillary sinus, but at lower rates in SCC of the larynx and of the tongue and oral cavity. MAGE-1 was frequently expressed in poorly differentiated SCC, somewhat less frequently in moderately differentiated SCC, and only infrequently in well-differentiated SCC. The expression levels of the other MAGE genes also varied with the anatomic site as well as the degree of differentiation. Our results suggest that specific immunotherapy against MAGE gene products may be useful for patients with head-and-neck carcinomas.