SSAT1 over-expression suppresses translation in mammalian cells through depletion of cellular polyamines: Important role of polyamines in regulation of translation.

Tuesday, October 09, 2012 — Poster Session I
1:00 p.m. – 3:00 p.m	Natcher Conference Center, Building 45	NIDCR	BIOCHEM-1

Authors

• Swati Dadhich
• Myung Hee Park

Abstract

The polyamines, putrescine, spermidine and spermine, are essential organic polycations, intimately involved in the regulation of cell proliferation. We investigated the cellular function of polyamines by over-expression of a key catabolic enzyme, spermidine/spermine N1-acetyltransferase1 (SSAT1). Transient co-transfection of HeLa cells with GFP and SSAT1 vectors suppressed GFP protein expression without lowering its mRNA level. Fluorescence single-cell imaging revealed specific inhibition of endogenous protein synthesis in the SSAT1 over-expressing cells, without any inhibition of synthesis of DNA or RNA. Over-expression of SSAT1 using a SSAT1 adenovirus led to rapid depletion of cellular spermidine and spermine, total inhibition of protein synthesis and an arrest in cell growth within 24h. The SSAT1 effect is due to depletion of spermidine and spermine, because stable polyamine analogs restored GFP expression and endogenous protein synthesis. Loss of polysomes with increased 80S monosomes in the polyamine-depleted cells suggests a direct role for polyamines in translation initiation.

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