Inhibition of queuine uptake in cultured human fibroblasts by phorbol-12,13-didecanoate

Journal Article · Fri Mar 01 00:00:00 EST 1985 · Cancer Res.; (United States)

OSTI ID:5613122

Elliott, M S; Trewyn, R W; Katze, J R

The modified base queuine is inserted posttranscriptionally into the first position of the anticodon of tyrosine tRNA, histidine tRNA, aspargine tRNA, and aspartic acid tRNA. Phorbol-12,13-didecanoate (PDD) effects a decrease in the queuine content of tRNA in cultured human foreskin fibroblasts. The present data suggest that this results from a PDD-mediated inhibition of queuine uptake. Nonsaturable uptake was observed for tritiated dihydroqueuine (rQT3) for up to 2 hr at 10 to 1000 nM concentrations, while saturation of uptake was observed after 3 to 4 hr. Lineweaver-Burke analysis of concentration versus uptake revealed biphasic uptake kinetics with high and low K/sub m/ components of approximately 350 and 30 nM, respectively. Competition by queuine of rQT3 uptake indicated that both compounds have equal affinity for the uptake mechanism. PDD inhibited rQT3 uptake but required 30 to 60 min of exposure before the uptake was completely blocked. The rQT3 efflux rate from cells was found to be 3 to 4 times greater than that of uptake, and PDD also inhibited the efflux reaction. The potential inhibitors furosemide, nitrobenzylthioinosine, ouabain, 7-methylguanine, 7-deazaguanine, guanine, guanosine, adenine, adenosine, hypoxanthine, and epidermal growth factor had no effect on rQT3 uptake. However, dipyridamole was immediately effective at reducing rQT3 uptake.

• Research Organization: Univ. of Tennessee Center for the Health Sciences, Memphis
• OSTI ID: 5613122
• Journal Information: Cancer Res.; (United States), Vol. 45:3
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
GUANINE
BIOCHEMICAL REACTION KINETICS
PHORBOL ESTERS
CARCINOGENESIS
FIBROBLASTS
MEMBRANE TRANSPORT
TRACER TECHNIQUES
TRANSFER RNA
TRITIUM COMPOUNDS
AMINES
ANIMAL CELLS
AROMATICS
AZAARENES
CARCINOGENS
CONNECTIVE TISSUE CELLS
ESTERS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PATHOGENESIS
PURINES
REACTION KINETICS
RNA
SOMATIC CELLS
550201* - Biochemistry- Tracer Techniques