We have previously shown that the DNA of the unicellular eukaryote T. brucei contains about 0.1% of a novel modified base, called J. The presence of J correlates with a DNA modification associated with the silencing of telomeric expression sites for the variant surface antigens of trypanosomes. Here we show that J is 5-((beta-D-glucopyranosyloxy)-methyl)-uracil (shortened to beta-D-glucosyl-hydroxymethyluracil), a base not previously found in DNA. We discuss putative pathways for the introduction of this base modification at specific positions in the DNA and the possible contribution of this modification to repression of surface antigen gene expression.

The relationship between the rat liver non-specific lipid-transfer protein (nsLTP) and the 58-kDa protein crossreactive with anti-nsLTP antibodies, was investigated by cDNA analysis. A 1945-bp cDNA clone was isolated which encodes a 58.7-kDa protein. This protein is identical to the 58-kDa immunoreactive protein determined by N-terminal sequence analysis of the purified 58-kDa protein. It consists of 546 amino acid residues, of which the 123 C-terminal residues are identical to the sequence of nsLTP. The N-terminal 400 amino acid residues of the 58.7-kDa protein were found to have 23.5% identity with the sequence of both mitochondria1 and peroxisomal rat 3-oxoacyl-CoA thiolases, including a hypothetical substrate-binding site. The cDNA insert hybridizes with 1.1-kb, 1.7-kb, 2.4-kb and 3.0-kb mRNA species in RNA isolated from various rat tissues and from Chinese hamster ovary (CHO) cells. Southern blot analysis suggests that these mRNA species are generated from a single gene. Mutant CHO cells, deficient in peroxisomes, lack nsLTP. We have found that the mRNA encoding nsLTP is still present in these cells, which suggests that the absence of this protein is related to the lack of peroxisomes.The non-specific lipid-transfer protein (nsLTP), also known as sterol-carrier protein 2 (SCP2), is a low-molecularmass protein (13.2 kDa) which catalyzes in vitro the transfer of a great variety of lipids, including cholesterol, between membranes [l -41. nsLTP was reported to stimulate various aspects of cholesterol metabolism, e.g. the microsomal conversion of lanosterol into cholesterol [5, 61, cholesterol esterification [6-81, bile acid formation [9] and steroid hormone synthesis [4,10,11]. The protein has been purified from bovine [12], rat [5, 12, 131, human [14] and goat [15] liver as well as from rat ovary [16]. The amino acid sequences of bovine [17], rat [18, 191 and human [20] liver nsLTP have about 90% identity. nsLTP purified from plants show no sequence similarity with the mammalian proteins [21-241.