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Molecular cloning and splicing isoforms of mouse p144, a homologue of CA150
M Shimada1, M Saito, T Katakai
1Course of Advanced Material Science, Graduate School of Science and Technology, Niigata University, 2-Igarashi, Niigata, 950-2181, Japan.
Abstract:
We previously characterized p144 bearing N-acetylglucosamine residues in a rat liver nuclear matrix fraction. Based on partial amino acid sequences of rat p144, mouse p144 cDNA was cloned and sequenced, and its amino acid sequence was predicted. The sequence revealed that p144 is a rat homologue of CA150, which is a transcription factor involved in Tat-activated human immunodeficiency virus type 1 transcription. The reported human CA150 consists of 1098 amino acids and has a leucine zipper-like motif in its carboxyl-region. However, a clone of mouse p144 cDNA encoded a CA150 consisting of 1,034 amino acids. The mouse CA150 was shorter by 64 amino acids than hitherto known human CA150 and lacked the leucine zipper-like motif. We designated the longer and shorter CA150 species as CA150a and CA150b, respectively. The partial nucleotide sequences of other mouse p144 cDNA clones were examined and it was found that some clones encode CA150a having a leucine zipper-like motif. It was suggested that CA150a and CA150b are splicing isoforms. All rat and mouse tissues examined contained transcripts for both CA150a and CA150b. Both transcripts were detected in human blood and Jurkat cells as well as mouse CD4(+) T-cells, which are the HIV-1-sensitive counterpart in humans.
Insights
Researchers identified mouse p144 as a homolog of human CA150, a transcription factor. They discovered two splicing isoforms, CA150a and CA150b, present in various tissues and relevant to HIV-1 sensitivity.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- p144, a rat protein, was previously identified with N-acetylglucosamine residues in the nuclear matrix.
- CA150 is a known transcription factor crucial for Tat-activated human immunodeficiency virus type 1 (HIV-1) transcription.
Purpose of the Study:
- To clone and sequence mouse p144 cDNA to elucidate its function and relationship to human CA150.
- To investigate the existence of CA150 isoforms and their tissue distribution.
Main Methods:
- Cloning and sequencing of mouse p144 cDNA.
- Amino acid sequence prediction and comparison with human CA150.
- Analysis of partial nucleotide sequences of other mouse p144 cDNA clones.
- Detection of transcripts in various rat, mouse, and human tissues/cells.
Main Results:
- Mouse p144 is a homolog of human CA150.
- Two splicing isoforms, CA150a (longer, with leucine zipper) and CA150b (shorter, lacking motif), were identified.
- Both isoforms are expressed in all examined rat and mouse tissues.
- Transcripts for both isoforms were found in human blood, Jurkat cells, and mouse CD4+ T-cells.
Conclusions:
- Mouse CA150 exists as at least two splicing isoforms, CA150a and CA150b.
- The differential expression of these isoforms may play a role in HIV-1 transcription regulation.
- The presence of transcripts in HIV-1 sensitive cells highlights their potential relevance in viral replication.