Herpes Simplex Virus Thymidine Kinase (HSV TK) PolyA Signal
Ultra-compact polyadenylation signal from HSV thymidine kinase gene, smallest commonly used polyA signal.
Origin: Herpes Simplex Virus Type 1 (HSV-1) thymidine kinase gene
Characteristics
Smallest commonly used polyA signal (~19-50 bp depending on variant). Minimal sequence provides basic polyadenylation function. Lower efficiency compared to bGH, SV40, and synthetic polyA signals. Yields lowest mRNA expression levels among common polyA elements in comparative studies. Simple structure without extensive upstream or downstream enhancer elements.
Applications
Extreme size-constraint applications where every base pair matters. Historical use in some viral vectors. Situations where reduced expression from polyA region is acceptable trade-off for size savings. Specialized applications requiring minimal genetic footprint.
Limitations
Lowest efficiency among commonly used polyA signals. Significantly reduced mRNA and protein expression compared to alternatives. Limited use in modern vectors due to availability of more efficient compact alternatives (synthetic polyA). Poor performance in stable expression contexts.