Preferential up-regulation of G2/M phase-specific genes by overexpression of the hyperactive form of NtmybA2 lacking its negative regulation domain in tobacco BY-2 cells.
Many G2/M phase-specific genes in plants contain mitosis-specific activator (MSA) elements, which act as G2/M phase-specific enhancers and bind with R1R2R3-Myb transcription factors. Here, we examined the genome-wide effects of NtmybA2 overexpression, one of the R1R2R3-Myb transcription factors in tobacco (Nicotiana tabacum). We used a custom-made 16-K cDNA microarray for comparative transcriptome analysis of transgenic tobacco BY-2 cell lines that overexpress NtmybA2 or its truncated hyperactive form. The microarray was also used to determine the transcript profile during the cell cycle in synchronized cultures of BY-2 cells. Combined microarray data from transgenic lines and synchronized cells revealed that overexpression of the truncated hyperactive form of NtmybA2, but not its full-length form, preferentially up-regulated many G2/M phase-specific genes in BY-2 cells. We determined promoter sequences of several such up-regulated genes and showed that all contain MSA-like motifs in the proximal regions of their promoters. One of the up-regulated genes, NtE2C, encoding for cyclin-specific ubiquitin carrier proteins, contained a single functional MSA-like motif, which specifically controlled the expression of a reporter gene in the G2/M phase in BY-2 cells. Furthermore, a genomic footprint experiment showed that the MSA element in the NtE2C promoter interacted with nuclear proteins in vivo. Therefore, we propose that the transcription of many G2/M phase-specific genes in tobacco is positively regulated by NtmybA2, in most cases through direct binding to the MSA elements.
Kato
Kiichi
K
Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
Gális
Ivan
I
Suzuki
Shiori
S
Araki
Satoshi
S
Demura
Taku
T
Criqui
Marie-Claire
MC
Potuschak
Thomas
T
Genschik
Pascal
P
Fukuda
Hiroo
H
Matsuoka
Ken
K
Ito
Masaki
M
D001483:Base Sequence; D002455:Cell Division / Q000235:genetics*; D018983:DNA Footprinting; D016195:G2 Phase / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006706:Homeostasis; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D020598:Proto-Oncogene Proteins c-myb / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D017384:Sequence Deletion; D014026:Nicotiana / Q000166:cytology / Q000235:genetics*; D015854:Up-Regulation / Q000235:genetics*
D050505:Mutant Proteins; D010940:Plant Proteins; D020598:Proto-Oncogene Proteins c-myb; D012333:RNA, Messenger