Construction and Operation of INSDC
In Japan, DDBJ Center internationally contributes as a member of INSDC to collect and to provide nucleotide sequence data with ENA/EBI in Europe and NCBI in USA.
DDBJ Center is officially certified to collect nucleotide sequences from researchers and to issue the internationally recognized accession number to data submitters. The accession number issued for each sequence data is unique on the database and internationally recognized to guarantee the submitter the property of the submitted and published data. Since DDBJ Center exchanges the released data with ENA/EBI and NCBI on a daily basis, the three data centers share virtually the same data at any given time. The virtually unified database is called INSD; International Nucleotide Sequence Database.
DDBJ collects sequence data mainly from Japanese researchers, but of course accepts data and issue the accession numbers to researchers in any other countries. 99% of INSD data from Japanese researchers are submitted through DDBJ.
See following links in detail.
Nucleotide sequence submission
Search and Analysis of sequence data
Collective Download from FTP site