Joan Pedersen-Lane

Processing of the intron-containing thymidylate synthase (td) gene of phage T4 is at the RNA level.

The interrupted T4 phage td gene, which encodes thymidylate synthase, is the first known example of an intron-containing prokaryotic structural gene. Analysis of td-encoded transcripts provides evidence in favor of maturation at the RNA level. Northern blotting with T4 RNA and with region-specific probes revealed three classes of RNA: diffuse premessage (ca. 2.5 kb), a low-abundance mature mRNA (ca. 1.3 kb), and an abundant free intron RNA (ca. 1.0 kb). The existence of covalently joined mature mRNA was suggested by hybridization and S1 protection experiments and was confirmed by primer extension analysis of the splice junction. In analogy to expression of interrupted eukaryotic genes, these results are consistent with an RNA processing model that would account for the direct gene transcript serving as precursor for both free intron RNA and a spliced mRNA that is colinear with the thymidylate synthase product.

Analysis of the thiol status of peripheral blood leukocytes in rheumatoid arthritis patients

Although the exact etiology of rheumatoid arthritis (RA) remains unknown, there is increasing evidence that reactive oxygen species and a pro‐oxidant/antioxidant imbalance are an important part of the pathogenesis of joint tissue injury. Flow cytometry was used to evaluate the thiol status [surface‐thiols and intracellular glutathione (iGSH)] of leukocytes from RA patients and controls. Levels of surface‐thiols and iGSH of leukocytes from RA patients were significantly lower than of leukocytes from controls. CD53, a glycoprotein of the tetraspanin superfamily, which coprecipitates with the GSH recycling enzyme γ‐glutamyl transpeptidase, was elevated significantly on leukocytes from RA patients compared with leukocytes from controls. Surface‐thiols and GSH play important roles in redox buffering of cells, providing protection from oxidative stress. The chronic inflammation of RA has been associated with oxidative stress, which is shown to cause a decline in the levels of cellular antioxidant sulfhydryls (R‐SH). As antioxidant‐protective levels also decline with age, the problem is compounded in older RA patients, who did have fewer R‐SH. Chronic stress can also have an effect on telomere lengths, determining cell senescence and longevity. Although telomeres shorten with increasing age, our flow cytometry studies indicate that accelerated shortening in telomere lengths occurs with increasing age of RA patients, suggesting premature cellular aging. The paradox is that lymphocytes from RA patients are believed to resist apoptosis, and we suggest that the elevated expression of CD53, which results from the increased oxidative stress, may protect against apoptosis.