The ancient mammalian KRAB zinc finger gene cluster on human chromosome 8q24.3 illustrates principles of C2H2 zinc finger evolution associated with unique expression profiles in human tissues

Table 2 Correlation between sequence and expression profile similarities

	Tissue	expression	matrix^b
Sequence similarity matrix^a	all KRAB-ZNF	8q24.3 KRAB-ZNF	Non-8q24.3 KRAB-ZNF
cDNA	0.27	0.62	0.15
Protein	0.39	0.62	0.38
ZNF	0.42	0.56	0.42
KRAB	0.22	0.71	0.16

^a Sequence similarity matrices are based on ClustalW alignments (IUB matrix for DNA or Gonnet matrix for protein sequences) and distance calculations using the Tamura-Nei method on DNA or the Poisson correction on the amino acid level, respectively, with the pairwise deletion option; calculated with MEGA4 (see Methods). Based on whole cDNA or full protein sequence or the ZNF or KRAB protein domains only.
^b Tissue expression matrices were calculated from the relative quantitative RT-PCR data using Pearson correlation distance.
Values represent Pearson correlation coefficients of matrix similarity comparisons (see Methods). All correlations are statistically significant (T-test, p < 0.0005), except cDNA and KRAB versus non-8q24.3 KRAB-ZNF (p = 0.068 and 0.062). Note that only ZNF genes with expressed KRAB domain from Figure 3 and available gene expression data were included.

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