Table 4.
“A-Tail” Length and Transcriptional Activity of the Different Alu Subfamilies
| Alu subfamily | % Alu transcriptsa | % Total Alus | Transcript enrichmentb | Long A-Tail Alus (%)c | Transcription/A-tail Factor | Expected (%)d | Observed (%)e |
|---|---|---|---|---|---|---|---|
| S + J | 66 | 82 | 0.80 | 58 (46) | 36.9 | 4 (23) | 0 (0) |
| Y | 33 | 17 | 1.96 | 34 (27) | 53.0 | 5 (33) | 5 (31) |
| Ya5 | 0.8 | 0.3 | 2.64 | 26 (21) | 54.4 | 5 (34) | 6 (38) |
| Yb8 | 0.5f | 0.2 | 2.50f | 8 (6) | 15.9 | 2 (10)f | 5 (31) |
| Total | 100 | 100 | — | 126 (100) | 160.2 | 16 (100) | 16 (100) |
Determined using previous data obtained from the isolation and sequencing of cDNAs derived from primary Alu transcripts (Shaikh et al. 1997).
Transcript enrichment is the increase in transcript proportion relative to copy number, also referred to in the Results section as transcription rate.
Data from Table 2 using the numbers of Alu elements retrieved from the human draft genome sequence with A-tail with ≥50 A.
Expected is obtained using the percentage of the transcription/A-tail factor (the product of the transcript enrichment and percentage of long A-tail members) to estimate the number of Alu elements from each subfamily when there are a total of 16.
Subfamily distribution of the Alu elements observed in 16 disease-causing insertions.
Because of the lack of transcript detection, an estimation was made on the basis of the AluYa5 subfamily copy number.