Structure and regulation of the salivary gland secretion protein gene Sgs-1 of Drosophila melanogaster.
The Drosophila melanogaster gene Sgs-1 belongs to the secretion protein genes, which are coordinately expressed in salivary glands of third instar larvae. Earlier analysis had implied that Sgs-1 is located at the 25B2-3 puff. We cloned Sgs-1 from a YAC covering 25B2-3. Despite using a variety of vectors and Escherichia coli strains, subcloning from the YAC led to deletions within the Sgs-1 coding region. Analysis of clonable and unclonable sequences revealed that Sgs-1 mainly consists of 48-bp tandem repeats encoding a threonine-rich protein. The Sgs-1 inserts from single lambda clones are heterogeneous in length, indicating that repeats are eliminated. By analyzing the expression of Sgs-1/lacZ fusions in transgenic flies, cis-regulatory elements of Sgs-1 were mapped to lie within 1 kb upstream of the transcriptional start site. Band shift assays revealed binding sites for the transcription factor fork head (FKH) and the factor secretion enhancer binding protein 3 (SEBP3) at positions that are functionally relevant. FKH and SEBP3 have been shown previously to be involved in the regulation of Sgs-3 and Sgs-4. Comparison of the levels of steady state RNA and of the transcription rates for Sgs-1 and Sgs-1/lacZ reporter genes indicates that Sgs-1 RNA is 100-fold more stable than Sgs-1/lacZ RNA. This has implications for the model of how Sgs transcripts accumulate in late third instar larvae.
Roth
G E
GE
Institut für Genetik, Freie Universität Berlin, 14195 Berlin, Germany. groth@genetik.biologie.fu-berlin.de
Wattler
S
S
Bornschein
H
H
Lehmann
M
M
Korge
G
G
D000595:Amino Acid Sequence; D000818:Animals; D018244:Chromosomes, Artificial, Yeast; D003001:Cloning, Molecular; D004331:Drosophila melanogaster / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D005967:Glue Proteins, Drosophila / Q000737:chemistry / Q000235:genetics*; D007814:Larva; D008969:Molecular Sequence Data; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012469:Salivary Glands / Q000502:physiology; D016415:Sequence Alignment; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D013912:Threonine
D005967:Glue Proteins, Drosophila; D013912:Threonine