Identification of three essential regions of hepatitis B virus X protein for trans-activation function.
The X protein of hepatitis B virus (HBV) consists of 154 amino acids and trans-activates various cellular and viral promoters and enhancers. To investigate the essential amino acid sequences of X protein for trans-activation function, various mutations were introduced into the X open reading frame and analysed for trans-activation activity by chloramphenicol acetyltransferase assay. The amino acid sequences 46-52 (especially Pro-46, His-49 and His-52), 61-69 (especially Cys-61, Gly-67 to Pro-68 and Cys-69) and 132-139 (especially Phe-132, Cys-137 and His-139) of HBV X protein were found to be essential for the trans-activation function. These three sequences are included in the conserved amino acid sequences among hepadna virus X proteins. The first one could form a domain-like structure characteristic of histidine/aspartic acid requirement. The second and the third are homologous to the Kunitz domain of Kunitz-type serine protease inhibitors. The amino acids 5-27 region was found to make no positive contribution to the trans-activation function like the last 12 amino acids in the carboxy-terminal region [Takada, S. & Koike, K. (1990). Proc. Natl. Acad. Sci. USA, 87, 5628-5632]. From these findings, the trans-activation function of X protein appears to be dependent on at least two types of domain-like structures.
Arii
M
M
Department of Gene Research, Cancer Institute, JFCR, Tokyo, Japan.
Takada
S
S
Koike
K
K
D000595:Amino Acid Sequence; D004252:DNA Mutational Analysis; D015870:Gene Expression; D006515:Hepatitis B virus / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000737:chemistry*; D015533:Transcriptional Activation; D014162:Transfection; D054334:Viral Regulatory and Accessory Proteins
D012333:RNA, Messenger; D011994:Recombinant Proteins; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein