JOURNAL ARTICLE

Polyamine and polyamine analog regulation of spermidine/spermine N1-acetyltransferase in MALME-3M human melanoma cells

M Fogel-Petrovic, N W Shappell, R J Bergeron, C W Porter
Journal of Biological Chemistry 1993 September 5, 268 (25): 19118-25
8360194
In MALME-3M human melanoma cells the polyamine analog N1,N12-bis(ethyl)spermine (BESPM) suppresses the key polyamine biosynthetic enzymes, ornithine and S-adenosylmethionine decarboxylase, and increases the polyamine catabolizing enzyme, spermidine/spermine N1-acetyl-transferase (SSAT) by more than 200-fold. In the present study increases in SSAT activity in MALME-3M cells treated with 10 microM BESPM were found to be accompanied by a substantial (up to 45-fold) accumulation of SSAT mRNA. By Northern blot analysis three RNA transcripts were found to hybridize with the coding region of human SSAT cDNA: a minor high molecular weight (approximately 3.5 kilobases) species designated form A and two lower molecular weight species designated forms B and C (approximately 1.5 and approximately 1.3 kilobases, respectively). Form A increased uniformly during BESPM treatment and was most obvious in nuclear RNA preparations. On the basis of size similarity to the transcribing region of the gene and hybridization with the coding region of SSAT cDNA and its prevalence in nuclear mRNA preparations, form A is thought to represent precursor SSAT RNA. Form C is present in control cells and increases steadily during treatment, whereas form B increases transiently during early treatment (1-3 h). By RNase H digestion assay, form B was found to have a 200-base pair longer poly(A) tract and as such may represent a precursor to form C. Accumulation of SSAT mRNA was found to be a result of increased gene transcription and stabilization of SSAT mRNA. Nuclear run-on studies indicated a 2-4-fold increase in the transcription rate of the SSAT gene. As indicated by actinomycin D studies, the SSAT mRNA half-life increased with BESPM treatment from 17 to 64 h. The natural polyamine, spermine, also increased SSAT mRNA (5.5-fold at 24 h) and behaved similarly to BESPM in inducing the appearance of the same three transcript forms. The polyamine was much less effective than the analog at increasing enzyme activity. Lowering intracellular polyamine pools with inhibitors of biosynthesis decreased basal SSAT mRNA levels by at least 70% indicating, that the gene can be down-regulated as well as up-regulated by polyamines. These findings indicate that SSAT represents a unique example of gene expression being positively influenced at the RNA level by polyamines and their analogs.

Full Text Links

Find Full Text Links for this Article

Discussion

You are not logged in. Sign Up or Log In to join the discussion.

Trending Papers

Remove bar
Read by QxMD icon Read
8360194
×

Save your favorite articles in one place with a free QxMD account.

×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"