Efficient transcription from the rice tungro bacilliform virus promoter requires elements downstream of the transcription start site.

Elements downstream of the transcription start site enhance the activity of the rice tungro bacilliform virus (RTBV) promoter in protoplasts derived from cultured rice cells. This enhancer region was located to the first 90 nucleotides of the RTBV leader sequence. Within this region, at least two components which act together to enhance expression from the RTBV promoter could be identified. One is a position- and orientation-independent DNA element within a CT-rich region, and the other is a position-dependent element. Either element was found to be capable of acting independently on a heterologous promoter. The enhancer activity of the DNA element correlates with specific binding of nuclear proteins. Nuclear proteins also recognize an RNA transcript covering the first 90 nucleotides of the RTBV leader.