1022-7954/01/3711- $25.00 © 2001
Russian Journal of Genetics, Vol. 37, No. 11, 2001, pp. 1247–1256. Translated from Genetika, Vol. 37, No. 11, 2001, pp. 1486–1496.
Original Russian Text Copyright © 2001 by Demakov, Gorchakov, Schwartz, Semeshin, Zhimulev.
The functional organization of interbands in poly-
tene chromosomes has been poorly understood (see [1–3]
for review). Based on the transcriptional activity exhib-
ited by some interbands and close similarity of chromo-
some band patterns in various
hypothesis was advanced that interbands contain per-
manently active genes of the cell metabolism (house-
keeping genes) . In the alternative models the band
and the interband were regarded as a functional unit.
There models considered the interband either a struc-
tural gene part with the regulatory region located in the
band  or a regulatory region of the gene located in
the band [5, 6]. Thus, the genetic composition of inter-
bands and their role in forming chromomere pattern of
chromosomes are still unclear and require investigation.
One of the approaches to understanding interband
functions consists in analyzing their molecular-genetic
organization. However, nucleotide sequences of inter-
bands cannot be precisely determined by standard tech-
niques due to their small size and low DNA content.
This problem can be circumvented using a method
based on electron microscopic (EM) analysis of poly-
tene chromosomes carrying inserted
most cases, new bands were detected in the transformed
chromosome regions. Moreover, it was convincingly
demonstrated that in some of the regions the new bands
were formed exclusively by the transposed sequences
[7, 8]. Based on these results, an appearance of a new
band was related to a transposon insertion in the inter-
band region. If the molecular structure of the transpo-
son is known, its DNA can be used as a probe for
screening genomic libraries and clone the interband
DNA adjacent to the transposon. Previously, nucleotide
sequences of three interbands were thus determined
[9, 10]. They were shown to be unique to the
genome, contain AT-rich sequences and polypu-
rine and polypirimidine tracts. No known genes or sig-
niﬁcant protein-coding sequences were found in the
DNA regions examined. DNA of these interband
regions was shown to be organized into nucleosomes
 and contain S/MAR sequences speciﬁcally associ-
ated with the nuclear matrix . However, it is still
unclear whether these features are characteristic for
other interbands in polytene chromosomes. To ascer-
tain this, examination of new bands is required.
In the present study, we cloned DNA of other two
interbands, 3A5/A6 and 60E8-9/E10, and compared
their sequences with each other and with the earlier
analyzed interbands [9, 10, 13]. In addition, EM analy-
sis of the X-chromosome interband 3C5-6/C7 region in
a strain carrying deletion
that removes part
of DNA from this region.
MATERIALS AND METHODS
Fly strains used in this work are listed in Table 1. Lar-
val salivary gland polytene chromosome preparations for
EM analysis were made as described earlier .
Analysis of DNA Interband Regions 3A5/A6, 3C5-6/C7,
and 60E8-9/E10 in Polytene Chromosomes
S. A. Demakov, A. A. Gorchakov, Yu. B. Schwartz, V. F. Semeshin, and I. F. Zhimulev
Institute of Cytology and Genetics, Russian Academy of Sciences, Novosibirsk, 630090 Russia;
fax: (3832) 33-12-78; e-mail: firstname.lastname@example.org
Received April 6, 2001
—Using electron microscopic (EM) data on the formation of a novel band from the
rial after its insertion in the interband and the procedure of
-target rescue, DNA interband regions 3A5/A6,
3C5-6/C7, and 60E8-9/E10 of
polytene chromosomes were cloned and sequenced.
EM analysis of the 3C region have shown that the formation of the full-size 3C5-6/C7 interband requires a 880-
bp DNA sequence removed by deletion
. A comparison of DNA sequences of six bands, two of which
were obtained in the present work and four were described earlier, demonstrated the uniqueness of each of them
genome and heterogeneity of their molecular organization. Interband 60E8-9/E10 contains
transcribed throughout the development, in particular in salivary glands. In the other interbands
examined 5' and 3' nontranslated gene regions are located. These results suggest that
contain both housekeeping genes and regulatory sequences of currently inactive genes from adjacent bands.