SpZ2-1(SpP3A1)

Function

SpZ2-1 (formerly SpP3A1) factor (Roger Anderson et al.,1994) codes for a Zn-finger DNA-binding protein. It binds in vitro specifically to the P3A target site in the skeletogenic SM50 gene and to the the similar target sequence in the CyIIIa gene.
It also binds in vitro to the closely spaced P3A sites in the Spec1 gene.
The function of this gene is unclear (Hoog et al., 1991).

Protein

The open reading frame of the SpZ2-1 sequence specifies a protein with a molecular mass of 42*10^3 (387 amino acids).
This protein has a high content of serine, theonine and proline, together about 29%.
The amino acid terminal region of the SpZ2-1 protein (positions 1-53) is strongly acidic and can function as a transcriptional activator region. A short strongly basic region (7/11 amino acids) appears after position 237.
The SpZ2-1 protein has no significant similarities with the other known DNA-binding proteins except for two regions which conform to the general form of Zn-finger motifs: Phe-X-Cys-X(2-4)-Cys-X3-Phe-X5-Leu-X2-His-X(3-5)-His [as described by Miller et al.(1985) and Berg (1988)].

Subcellular location

Egg cytoplasm and pronuclus, embryonic nuclei (Zeller et al., 1995).

Expression Pattern

SpZ2-1 factor is present in unfertilyzed eggs, and enters the embryonic nuclei early in development. There are about 300 copies of SpZ2-1 mRNA per egg.
At 4h postfertilization there are approximately 600 copies of the SpZ2-1 mRNA per embryo of average length about 2,5 kb.
At 24h there are about 2000 copies of SpZ2-1 mRNA per embryo (at that stage - about 4 molecules per/cell).
After that the level of transcripts begins to fall until the early gastrula, when they are not detected (Hoog et al., 1991).

The average SpZ2-1 protein levels (molecules/nucleus)
Method: Immunological blot reaction
Reference: Zeller et al., 1995

Stage Egg pronuleus 5 hr 10 hr 24 hr 36 hr 48 hr

Level 1.46*10^5 1.5*10^5 4*10^4 2.5*10^3 1.7*10^3 <1.1