Cis-regulatory elements of the mitotic regulator, string/Cdc25.
Mitosis in most Drosophila cells is triggered by brief bursts of transcription of string (stg), a Cdc25-type phosphatase that activates the mitotic kinase, Cdk1 (Cdc2). To understand how string transcription is regulated, we analyzed the expression of string-lacZ reporter genes covering approximately 40 kb of the string locus. We also tested protein coding fragments of the string locus of 6 kb to 31.6 kb for their ability to complement loss of string function in embryos and imaginal discs. A plethora of cis-acting elements spread over >30 kb control string transcription in different cells and tissue types. Regulatory elements specific to subsets of epidermal cells, mesoderm, trachea and nurse cells were identified, but the majority of the string locus appears to be devoted to controlling cell proliferation during neurogenesis. Consistent with this, compact promotor-proximal sequences are sufficient for string function during imaginal disc growth, but additional distal elements are required for the development of neural structures in the eye, wing, leg and notum. We suggest that, during evolution, cell-type-specific control elements were acquired by a simple growth-regulated promoter as a means of coordinating cell division with developmental processes, particularly neurogenesis.
Lehman
D A
DA
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
Patterson
B
B
Johnston
L A
LA
Balzer
T
T
Britton
J S
JS
Saint
R
R
Edgar
B A
BA
D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D004330:Drosophila / Q000196:embryology* / Q000235:genetics*; D029721:Drosophila Proteins; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000502:physiology*; D004627:Embryonic Induction; D018507:Gene Expression Regulation, Developmental; D008938:Mitosis; D009420:Nervous System / Q000196:embryology; D010749:Phosphoprotein Phosphatases / Q000235:genetics* / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D017027:Protein Tyrosine Phosphatases; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic; D020687:cdc25 Phosphatases
D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D010749:Phosphoprotein Phosphatases; D017027:Protein Tyrosine Phosphatases; D020687:cdc25 Phosphatases; C059217:stg protein, Drosophila